2005 antilock brakes

2005 BRAKES

L300

SCHEMATIC AND ROUTING DIAGRAMS

ABS SCHEMATICS

Fig. 1: EBCM Power, Ground, Serial Data, and Switches Courtesy of GENERAL MOTORS CORP.

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Monday, May 09, 2011 11:15:21 AM © 2006 Mitchell Repair Information Company, LLC.

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Monday, May 09, 2011 11:15:34 AM Page 1 © 2006 Mitchell Repair Information Company, LLC.

Fig. 2: Wheel Speed Sensors Courtesy of GENERAL MOTORS CORP.

COMPONENT LOCATOR

ABS COMPONENT VIEWS

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Fig. 3: Identifying ABS Components Courtesy of GENERAL MOTORS CORP.

Callouts For Fig. 3

ABS CONNECTOR END VIEWS

Electronic Brake Control Module (EBCM)

Callout Component Name1 Wheel Speed Sensor (WSS)- LR2 Right Heated Seat/Traction Switch3 Wheel Speed Sensor (WSS)- LF4 Electronic Brake Control Module (EBCM)5 Wheel Speed Sensor (WSS)- RF6 Wheel Speed Sensor (WSS)- RR

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Connector Part Information � 15326596 � 31-Way F Standard Power Timer Sealed (BK)

Pin Wire Color Circuit No. Function

1 WH 883 Right Rear Wheel Speed Sensor Low Reference

2 BN 882 Right Rear Wheel Speed Sensor Signal

3 TN 833Right Front Wheel Speed Sensor Low Reference

4 - - Not Used5 D-GN 872 Right Front Wheel Speed Sensor Signal

6 YE 873Left Front Wheel Speed Sensor Low Reference

7 L-BU 830 Left Front Wheel Speed Sensor Signal

8 RD 885 Left Rear Wheel Speed Sensor Low Reference

9 BK 884 Left Rear Wheel Speed Sensor Signal10 - - Not Used11 L-BU 1276 ABS Serial Data K-Line12 - - Not Used13 OG/BK 463 Requested Torque Signal14 L-BU 20 Stop Lamp Switch Signal15 PK 339 Ignition 1 Voltage16 BK 150 Ground17 RD 702 Battery Positive Voltage18 OG 1002 Battery Positive Voltage19 BK 150 Ground20 L-BU 832 Traction Control Active Signal21 L-GN 867 ABS Indicator Failure Control

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Right Heated Seat/Traction Switch

Stop Lamp Switch

22-25 - - Not Used26 WH 1909 Right Front Wheel Speed Sensor Signal27 TN/BK 464 Delivered Torque Signal28 WH 2192 Traction Ready Indicator Control29 - - Not Used30 WH 121 Engine Speed Signal31 L-BU 1788 Traction Control Switch Signal

Connector Part Information � 12047886 � 8-Way F Metri-Pack 150 Series (BK)

Pin Wire Color Circuit No. FunctionA BN 641 Ignition 3 VoltageB D-BU 1660 Traction Control Indicator ControlC L-BU 1788 Traction Control Switch Signal

D GY 8 Instrument Panel Lamps Dimmer Switch Signal

E BK 550 GroundF PK/BK 1503 Passenger Heated Seat High/Low SignalG L-GN 559 Heated Occupant Sensor SignalH - - Not Used

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Wheel Speed Sensor (WSS) - LF

Connector Part Information � 15317343 � 4-Way F Standard Power Timer (BK)

Pin Wire Color Circuit No. Function1-2 - - Not Used3 L-BU 20 Stop Lamp Switch Signal4 OG 540 Battery Positive Voltage

Connector Part Information � 15358647 � 2-Way M (NA)


1 YE 873Left Front Wheel Speed Sensor Low Reference

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Wheel Speed Sensor (WSS) - LR

Wheel Speed Sensor (WSS) - RF

2 D-GN 830 Left Front Wheel Speed Sensor Signal

Connector Part Information � 12052644 � 2-Way F Metri-Pack 150 Series Sealed (GN)


A BK 884Left Rear Wheel Speed Sensor Low Reference

B RD 885 Left Rear Wheel Speed Sensor Signal

Connector Part Information � 15358648 � 2-Way M (NA)


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Wheel Speed Sensor (WSS) - RR

DIAGNOSTIC INFORMATION AND PROCEDURES

DIAGNOSTIC STARTING POINT - ANTILOCK BRAKE SYSTEM

Begin the system diagnosis with Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check will provide the following information:

� The identification of the control modules which command the system

� The ability of the control modules to communicate through the serial data circuit

� The identification of any stored diagnostic trouble codes (DTCs) and their status

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

SCAN TOOL OUTPUT CONTROLS

Scan Tool Output Controls

1 TN 833 Right Front Wheel Speed Sensor Low Reference

2 D-GN 872 Right Front Wheel Speed Sensor Signal

Connector Part Information � 12052644 � 2-Way F Metri-Pack 150 Series Sealed (GY)


A BN 882 Right Rear Wheel Speed Sensor Low Reference

B WH 883 Right Rear Wheel Speed Sensor Signal

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SCAN TOOL DATA LIST

The electronic brake control module (EBCM) Scan Tool Data Lists contain all the antilock brake system related parameters that are available on the scan tool. The parameters in the list are arranged in alphabetical order. The column, Data List, indicates the location of the parameter within the scan tool menu selections.

Use the EBCM Scan Tool Data Lists as directed by a diagnostic table or in order to supplement the diagnostic procedures. Begin all the diagnostic procedures with the ABS Diagnostic Starting Point. Use the EBCM Scan Tool Data Lists only after the following is determined:

� There is no published DTC procedure nor published symptom procedure for the customer concern.

OR

� The DTC or symptom diagnostic procedure indicated by the diagnostic system check does not resolve the customer concern.

The Typical Data Values are obtained from a properly operating vehicle under the conditions specified in the first row of the Scan Tool Data List table. Comparison of the parameter values from the suspect vehicle with the Typical Data Values may reveal the source of the customer concern.

Scan Tool Output Control

Additional Menu Selection(s) Description

ABS Warning Lamp Lamp Tests Commands the ABS indicator ON and OFF.Automated Bleed Procedure

Automated Bleed Used in order to bleed the ABS hydraulics.

Automated Test Procedure Automated Test

Used in order to activate the ABS solenoids and pump motor.

LF Inlet Valve Solenoid Solenoid Test Commands the solenoid ON and OFF.

LF Outlet Valve Solenoid Solenoid Test Commands the solenoid ON and OFF.

Low Traction Lamp Lamp Tests Commands the Low Traction Lamp ON and OFF.LR Inlet Valve Solenoid Solenoid Test

Commands the solenoid ON and OFF.

LR Outlet Valve Solenoid Solenoid Test

Commands the solenoid ON and OFF.

RF Inlet Valve Solenoid Solenoid Test Commands the solenoid ON and OFF.

RF Outlet Valve Solenoid Solenoid Test Commands the solenoid ON and OFF.

RR Inlet Valve Solenoid

Solenoid Test Commands the solenoid ON and OFF.

RR Outlet Valve Solenoid

Solenoid Test Commands the solenoid ON and OFF.

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The ID Information menu is located on the EBCM main screen.

Body Control Module (BCM)

EBCM Scan Tool Data List

Scan Tool Parameter Data List Units Displayed Typical Data ValueIgnition ON, engine OFF, brake fluid level normal, and park brake released.

ABS Fault ABS/TCS Data Yes/No NoBattery 1 ABS/TCS Data Volts 11.5 Volts

Park Brake Switch Switch Inputs Off/On OffTraction Active ABS/TCS Data No/Yes No

Traction Control Status ABS/TCS Data On/Off OnTraction LED Command ABS/TCS Data On/Off OnTraction LED Feedback ABS/TCS Data High/Low LowLow Brake Fluid Level Switch Inputs No/Yes No

Scan Tool Parameter Data List Units Displayed Typical Data ValueIgnition is ON, engine OFF, and vehicle is stationary

Battery Voltage ABS Volts -Brake lamp Switch State ABS On/Off OffDelivered Engine Torque ABS percent -

Engine Speed ABS RPM 0Left Front Wheel Speed ABS km/h or mph 0Left Rear Wheel Speed ABS km/h or mph 0LF Inlet Valve Solenoid ABS Apply/Released Released

LF Outlet Valve Solenoid ABS Apply/Released ReleasedLF Valve Solenoids ABS Apply/Released Released

LR Inlet Valve Solenoid ABS Apply/Released ReleasedLR Outlet Valve Solenoid ABS Apply/Released Released

LR Valve Solenoids ABS Apply/Released ReleasedRF Inlet Valve Solenoid ABS Apply/Released Released

RF Outlet Valve Solenoid ABS Apply/Released ReleasedRF Valve Solenoids ABS Apply/Released ReleasedReturn Pump Relay ABS - -

Right Front Wheel Speed ABS km/h or mph 0Right Rear Wheel Speed ABS km/h or mph 0RR Inlet Valve Solenoid ABS Apply/Released Released

RR Outlet Valve Solenoid ABS Apply/Released Released

RR Valve Solenoids ABS Apply/Released ReleasedTCS Switch State ABS On/Off Off

Valve Relay ABS Volts -

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SCAN TOOL DATA DEFINITIONS

Data Display/Definitions

The Scan Tool Data Display/Definitions contains a brief description of all the ABS data parameters. The menus available depend on the number and type of system on the vehicle and are listed below in alphanumeric order.

� ABS DATA

� TCS DATA

Battery Voltage

The scan tool will display the battery voltage at the electronic brake control module (EBCM).

Brake Lamp Switch

The scan tool will display Applied or Released depending on the state of the brake switch.

Delivered Engine Torque

The scan tool will display.

Engine Speed

The scan tool will display between 0-10,200 RPM which is a digital tachometer display.

Left Front Wheel Speed

The scan tool displays 0-255 km/h or (0-158 mph). The scan tool displays the actual speed of the left front wheel.

Left Rear Wheel Speed

The scan tool displays 0-255 km/h or (0-158 mph). The scan tool displays the actual speed of the left rear wheel.

LF Inlet Valve Solenoid

The scan tool will display Apply or Released. The scan tool displays the commanded state of the LF inlet solenoid valve.

LF Outlet Valve Solenoid

The scan tool will display Apply or Released. The scan tool displays the commanded state of the LF

Valve Relay State ABS On/Off On

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outlet solenoid valve.

LF Valve Solenoid

The scan tool will display Apply or Released. The scan tool displays the commanded state of the LF solenoid valve.

LR Inlet Valve Solenoid

The scan tool displays Apply or Released. The scan tool displays the commanded state of the LR inlet solenoid valve.

LR Outlet Valve Solenoid

The scan tool displays Apply or Released. The scan tool displays the commanded state of the LR outlet solenoid valve.

LR Valve Solenoid

The scan tool will display Apply or Released. The scan tool displays the commanded state of the LR solenoid valve.

RF Inlet Valve Solenoid

The scan tool displays Apply or Released. The scan tool displays the commanded state of the RF inlet solenoid valve.

RF Outlet Valve Solenoid

The scan tool displays Apply or Released. The scan tool displays the commanded state of the RF outlet solenoid valve.

RF Valve Solenoid

The scan tool will display Apply or Released. The scan tool displays the commanded state of the RF solenoid valve.

Return Pump Motor Relay

The scan tool will display On or Off.

Right Front Wheel Speed

The scan tool displays 0-255 km/h or (0-158 mph). The scan tool displays the actual speed of the right front wheel.

Right Rear Wheel Speed

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The scan tool displays 0-255 km/h or (0-158 mph). The scan tool displays the actual speed of the right rear wheel.

RR Inlet Valve Solenoid

The scan tool displays Apply or Released. The scan tool displays the commanded state of the RR inlet solenoid valve.

RR Outlet Valve Solenoid

The scan tool displays Apply or Released. The scan tool displays the commanded state of the RR outlet solenoid valve.

RR Valve Solenoid

The scan tool displays Apply or Released. The scan tool displays the commanded state of the RR solenoid valve.

TCS Switch State

The scan tool displays On or Off. The scan tool will display the state of the Traction Control Switch.

Valve Relay

The scan tool displays.

Valve Relay State

The scan tool will display On/Off depending on the state of the relay.

DTC C0035-C0051

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Fig. 4: Wheel Speed Sensors Wiring Schematic Courtesy of GENERAL MOTORS CORP.

Circuit Description

As the wheels spin, each wheel speed sensor produces an AC signal. The electronic brake control module (EBCM) uses the frequency of the AC signals to calculate each wheel speed.

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DTC Descriptors

This diagnostic procedure supports the following DTCs:

� DTC C0035 Left Front Wheel Speed Sensor Circuit Malfunction

� DTC C0036 Left Front Wheel Speed Sensor Circuit Range/Performance

� DTC C0040 Right Front Wheel Speed Sensor Circuit Malfunction

� DTC C0041 Right Front Wheel Speed Sensor Circuit Range/Performance

� DTC C0045 Left Rear Wheel Speed Sensor Circuit Malfunction

� DTC C0046 Left Rear Wheel Speed Sensor Circuit Range/Performance

� DTC C0050 Right Rear Wheel Speed Sensor Circuit Malfunction

� DTC C0051 Right Rear Wheel Speed Sensor Circuit Range/Performance

Conditions for Running the DTC

� The ignition is ON.

� The vehicle speed is greater than 40 km/h (25 mph).

Conditions for Setting the DTC

Any of the following conditions may cause the DTC to set.

� The EBCM detects an open wheel speed sensor circuit.

� The EBCM detects a shorted wheel speed sensor circuit.

� The EBCM detects the absence of a wheel speed sensor signal.

� The EBCM detects an erratic wheel speed sensor signal.

Action Taken When the DTC Sets

� The EBCM disables the antilock brake system/traction control system (TCS) and may disable the dynamic rear proportion (DRP), if more than one wheel speed sensor (WSS) DTC is set.

� The ABS indicator turns ON.

� The traction off indicator turns ON.

� The brake warning indicator may turn ON.

Conditions for Clearing the DTC

The Conditions for Setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Diagnostic Aids

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs ,Testing for Electrical Intermittents , and Wiring Repairs in Wiring Systems.

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If the customer concern is that the ABS indicator is ON only during humid conditions such as rain, snow, or vehicle wash, thoroughly inspect the WSS circuits for signs of water intrusion. Use the following procedure in order to help isolate the problem area:

1. Spray the suspected area with a 5 percent salt water solution.

2. Operate the vehicle at a speed greater than 13 km/h (8 mph) for at least 30 seconds.

Repair or replace the suspect harness if the DTC sets.

DTC C0035-C0051 Step Action Values Yes No

Schematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

-

Go to Step 2

Go to Diagnostic

System Check - Vehicle in

Vehicle DTC Information

2

1. Use the scan tool to clear the DTCs.

2. Turn OFF the ignition for 5 seconds.

3. Turn ON the ignition.

4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

40 km/h (25 mph)

Go to Step 3 Go to

Diagnostic Aids

3

1. Turn OFF the ignition.

2. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.

3. Disconnect the wheel speed sensor (WSS) connector.

4. Use a DMM in order to measure the resistance across the WSS.

Does the resistance measure within the specified range?

800-1,700 ohms

Go to Step 4 Go to Step 8

4

1. Slowly spin the wheel by hand.

2. Use a DMM in order to measure the AC voltage across the WSS as the wheel spins.

Does the AC voltage measure greater than the

100 mV

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DTC C0060-C0095

specified value? Go to Step 5 Go to Step 8

5

Inspect for poor connections at the harness connector of the WSS. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?

-


6

1. Disconnect the electronic brake control module (EBCM) harness connector.

2. Test the WSS circuits for the following:

� An open

� A short to ground

� A short to voltage

� Shorted together

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?

-


7

Inspect for poor connections at the harness connector for the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?

-


8

Replace the WSS. Refer to Wheel Speed Sensor Replacement - Front or Wheel Speed Sensor Replacement - Rear. Did you complete the replacement?

-

Go to Step 10 -

9

Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?

-

Go to Step 10 -

10

1. Use the scan tool Clear All Class 2 DTCs function to clear all of the DTCs from all modules.




Does the DTC reset?

-

Go to Step 2 System OK

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Circuit Description

The electronic brake control module (EBCM) performs several self-tests for internal problems which may affect proper operation. The antilock brake system (ABS) control module controls valve function by grounding the solenoid circuit when necessary.

DTC Descriptors


� DTC C0060 Left Front ABS Solenoid #1 Circuit Malfunction

� DTC C0065 Left Front ABS Solenoid #2 Circuit Malfunction

� DTC C0070 Right Front ABS Solenoid #1 Circuit Malfunction

� DTC C0075 Right Front ABS Solenoid #2 Circuit Malfunction

� DTC C0080 Left Rear ABS Solenoid #1 Circuit Malfunction

� DTC C0085 Left Rear ABS Solenoid #2 Circuit Malfunction

� DTC C0090 Right Rear ABS Solenoid #1 Circuit Malfunction

� DTC C0095 Right Rear ABS Solenoid #2 Circuit Malfunction


The ignition is ON.


The ABS control module detects an open, short to ground, or short to voltage on the solenoid circuits inside the control module.


� The EBCM disables the ABS/dynamic rear proportion (DRP)/traction control system (TCS).




Certain conditions that may cause this DTC to set cannot be cleared. Other conditions that may cause this DTC to set may be cleared, at least temporarily, by using the scan tool Clear DTCs function.

Diagnostic Aids

Replace the EBCM if this DTC continues to set intermittently.

DTC C0060-C0095 Step Action Yes No

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DTC C0110

1


Go to Step 2

Go to Diagnostic System Check -

Vehicle in Vehicle DTC Information

2Use a scan tool in order to clear the DTCs. Can the DTC be cleared? Go to Step 3 Go to Step 4

3



Does the DTC reset? Go to Step 4 Go to Diagnostic

Aids

4

Replace the electronic brake control module (EBCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? Go to Step 5 -

5





Does the DTC reset? Go to Step 3 System OK

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Fig. 5: ABS Pump Motor Control Wiring Schematic Courtesy of GENERAL MOTORS CORP.

Circuit Description

Ground is continuously supplied to the low side of the antilock brake system (ABS) pump motor. The electronic brake and traction control module (EBTCM) activates the ABS pump motor by energizing the pump motor relay, allowing battery voltage to the high side of the motor.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0110 Pump Motor Circuit


The ignition is ON.


The electronic brake control module (EBCM) detects an open or shorted pump motor circuit, or a fault in the pump motor relay.


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� The ABS telltale will be ON.

� The ABS control module will disable the ABS, the traction control system (TCS), and the dynamic rear proportion (DRP).


The Conditions for Setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Diagnostic Aids

� The pump relay and motor are NOT serviceable.

� The valve assembly, with control module, must be replaced.

DTC C0110 Step Action Yes No


1


Go to Step 2



2 Use a scan tool in order to clear the DTCs. Does the DTC reset? Go to Step 3

Go to Diagnostic Aids

3

1. Separate the electronic brake control module (EBCM) from the brake pressure modulator valve (BPMV). Refer to Electronic Brake Control Module Replacement.

2. Inspect for poor connections at the pump motor connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition? Go to Step 5 Go to Step 4

4

Replace the EBCM and the BPMV. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming and Brake Pressure Modulator Valve (BPMV) Replacement.Did you complete the replacements?

IMPORTANT:New ABS control modules will automatically set DTC C0551 when installed. To clear DTC C0551, new modules must be configured with the correct engine and transmission option bit. Refer to Electronic Brake Control Module Replacement.

Go to Step 5 -

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DTC C0121


Circuit Description

The antilock brake system (ABS) control module uses a relay to control the valve solenoids. When the ignition is in the Run position, the module energizes the relay winding to switch the battery voltage that supplies the solenoids. The module will disable the relay when the ignition is OFF, or a fault is detected.

DTC Descriptor


DTC C0121 Valve Relay Circuit

5

1. Use a scan tool in order to clear the DTCs.



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The ignition is ON.


� The control module commands the relay ON, but does not sense battery voltage at the solenoids.

� The control module commands the relay OFF, and senses battery voltage at the solenoids.


� The ABS telltale turns ON.


Diagnostic Aids

This relay is inside the ABS control module and is NOT serviceable.

Test Description

The number below refers to step number on the diagnostic table.

2: This step determines if the DTC is current.



1


Go to Step 2



2

1. Install a scan tool.

2. Turn ON the ignition, with the engine OFF.

3. Use the scan tool in order to clear the DTCs.


Aids

3

1. Disconnect the electronic brake control module (EBCM) harness connector.

2. Test the battery positive voltage circuit for an open, high resistance, or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

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DTC C0141-C0156

Circuit Description

The UHFB supplies the solenoid circuits with battery voltage when the ignition is in the RUN position. The ABS control module controls the valve function by grounding the solenoid circuit when necessary.

The #1 solenoids are prime valves. The #2 solenoids are isolation valves.

DTC Descriptors


� DTC C0141 Left TCS Solenoid #1 Circuit Malfunction

� DTC C0146 Left TCS Solenoid #2 Circuit Malfunction

� DTC C0151 Right TCS Solenoid #1 Circuit Malfunction

� DTC C0156 Right TCS Solenoid #2 Circuit Malfunction


The ignition is turned ON.


The DTC will set if the ABS control module detects an open, short to ground, or short to voltage on the solenoid circuits inside the control module.


� The ABS telltale will be ON.


Did you find and correct the condition? Go to Step 5 Go to Step 4

4

Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? Go to Step 5 -

5




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The condition for the DTC is no longer present and the DTC is cleared with a scan tool.

Diagnostic Aids

The ABS control module must be replaced.

DTC C0141-C0156

DTC C0161

Step Action Yes No

1


Go to Step 2



2Use a scan tool in order to clear the DTCs. Can the DTC be cleared? Go to Step 3 Go to Step 4

3Start the engine and allow the engine to idle. Does the DTC reset? Go to Step 4


4


5




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Fig. 7: Stop Lamp Switch Wiring Schematic Courtesy of GENERAL MOTORS CORP.

Circuit Description

The normally-open stop lamp switch supplies battery voltage to the ABS control module when the brake pedal is depressed.

DTC Descriptor


DTC C0161 ABS/TCS Brake Switch Circuit


The DTC will set if the ABS control module detects an open in circuit 20.

Diagnostic Aids

Inspect the wiring, the components, and the connectors for the following:

IMPORTANT: When DTC C0161 sets, the ABS control module will NOT disable the ABS, the traction control system (TCS), and the dynamic rear proportion (DRP).

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� Proper connection

� Backed-out terminals

� Broken connector locks

� Corrosion in the connectors/terminals

� Burned, chafed, or pinched wiring

� A broken wire inside the insulation

� Loose components

� Both brake lamp bulbs burned out

Test Description

The numbers below refer to the step numbers on the diagnostic table.

3: This DTC detects an open stop lamp switch signal circuit from the stop lamp side of the splice pack to the electronic brake control module (EBCM).

4: The EBCM sources 5 volts on the stop lamp switch signal circuit. This small voltage has a ground path through the stop lamp bulbs. This DTC sets if the path to ground is open.


Connector End View Reference: ABS Connector End Views or Lighting Systems Connector End Views in Lighting Systems

1


Go to Step 2



2

1. Press the brake pedal.

2. With the scan tool, observe the Brake Switch Status parameter in the ABS data list.

Does the Brake Switch Status parameter display Applied? Go to Step 4 Go to Step 3

3

Test the signal circuit of the stop lamp switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 9 Go to Step 7

4 Press the brake pedal. Are all of the stop lamps OFF? Go to Step 5


5

Test the feed circuit of the stop lamps for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 9 Go to Step 6 Test the ground circuit of the stop lamps for an open or

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DTC C0236

Fig. 8: Traction Control Circuit Courtesy of GENERAL MOTORS CORP.

Circuit Description

The engine control module (ECM) provides the electronic brake and traction control module (EBTCM) with engine RPM data so that it can determine traction control operation.

6high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 9


7

Inspect for poor connections at the harness connector of the electronic brake control module (EBCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 9 Go to Step 8

8

Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? Go to Step 9 -

9




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DTC Descriptor


DTC C0236 TCS RPM Signal Circuit


The ignition is ON.


� The DTC will set if the ABS control module detects an open or short in the RPM signal circuit.

� The EBTCM does not receive a RPM signal one second after the engine has been started.


� The EBTCM disables the traction control system (TCS).

� The TCS enable lamp is turned OFF.


� The condition for the DTC is no longer present and the DTC is cleared with a scan tool.

� The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids

Inspect the wiring, the components, and the connectors for the following:

� Proper connection



� Corrosion in the connectors/terminals

� Burned, chafed, or pinched wiring


� Loose components

� Both brake lamp bulbs burned out


Schematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views or Lighting Systems Connector End Views in Lighting Systems

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DTC C0241

1


Go to Step 2



2

1. Connect the scan tool.

2. Start the vehicle.

3. Use the scan tool in order to monitor the engine speed in the ABS data display.

Does the scan tool display proper RPM at idle?Go to Diagnostic

Aids Go to Step 3

3Use the scan tool to monitor the engine speed in the Engine Data List. Does the scan tool display proper RPM at idle? Go to Step 6 Go to Step 4

4

Test the RPM signal circuit for an open or short. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 7 Go to Step 5

5


6

Replace the engine control module (ECM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? Go to Step 7 -

7




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Circuit Description

The electronic brake and traction control module (EBTCM) and the engine control module (ECM) simultaneously control the traction control. The ECM reduces the amount of torque supplied to the drive wheels by retarding spark timing and selectively turning OFF the fuel injectors. The EBTCM actively applies the brakes to the front wheels in order to reduce torque.

The electronic brake control module (EBCM) sends a requested torque message via pulse width modulated (PWM) signal to the ECM. The duty cycle of the signal is used to determine how much engine torque the EBTCM is requesting the ECM to deliver. Normal values are between 10-90 percent duty cycle. The signal should be at 90 percent when traction control is not active and at lower values during traction control activations. The ECM supplies a pull up voltage of 5 volts that the EBTCM switches to ground to create the signal.

DTC Descriptor


DTC C0241 Powertrain Control Module (PCM) Indicated Torque Requested Malfunction



� The engine is running.


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� The EBTCM does not receive the delivered torque signal, open, or shorted circuit.

� An incorrect delivered torque signal is detected by the EBTCM.


� Traction control will be disabled.


Diagnostic Aids

� It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.

� Thoroughly inspect any circuitry that may be causing the complaint for the following conditions:


� Improper mating

� Broken locks

� Improperly formed or damaged terminals

� Poor terminal-to-wiring connections

� Physical damage to the wiring harness

� The following conditions may cause an intermittent malfunction:

� A poor connection

� Rubbed-through wire insulation


� If the customer comments reflect that the amber ABS/TCS indicator is ON only during moist environmental conditions (rain, snow, vehicle wash), inspect all the wheel speed sensor (WSS) circuitry for signs of water intrusion. If the DTC is not current, clear all DTCs and simulate the effects of water intrusion by using the following procedure:

1. Spray the suspected area with a 5 percent saltwater solution.

Add 2 teaspoons of salt to 12 ounces of water to make a 5 percent saltwater solution.

2. Test drive the vehicle over various road surfaces (bumps, turns, etc.) above 40 km/h (25 mph) for at least 30 seconds.

3. If the DTC returns, replace the suspected harness.

� If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

DTC C0241 Step Action Values Yes No


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1


-

Go to Step 2

Go to Diagnostic



2



3. Start the engine.

Does the DTC set?

-

Go to Step 3 Go to

Diagnostic Aids

3

With the engine running, use the scan tool in order to monitor the torque requested in the engine control module (ECM) data display. Does the scan tool show a torque requested value between the specified value?

90-100%Go to

Diagnostic Aids Go to Step 4

4

1. Disconnect the electronic brake and traction control module (EBTCM).

2. Using a DMM, measure the voltage on the delivered torque signal circuit.

Is the voltage measured within the specified range?

4-6 V


5

Test the requested torque signal circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?

-


6


2. Inspect for poor connections at the harness connector of the EBTCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

-


7

Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?

-

Go to Step 10 Go to Step 9 IMPORTANT:New ABS control modules will automatically set DTC C0551 when installed. To clear

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DTC C0244

8 Replace the electronic brake control module (EBCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.Did you complete the replacement?

correct engine and transmission option bit. Refer to ABS programming on the scan tool.

-

Go to Step 10 -

9 Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.Did you complete the replacement?

IMPORTANT:Perform the setup procedure for the ECM.

-

Go to Step 10 -

10





Does the DTC reset?

-


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Circuit Description

The electronic brake and traction control module (EBTCM) and the engine control module (ECM) simultaneously control the traction control. The ECM reduces the amount of torque supplied to the drive wheels by retarding spark timing and selectively turning OFF the fuel injectors. The EBTCM actively applies the brakes to the front wheels in order to reduce torque.

The electronic brake control module (EBCM) supplies approximately 12 volts through an internal resistor to the ECM on the delivered torque signal circuit. The ECM toggles this voltage to ground in order to create the delivered torque signal at the EBCM. A signal with a frequency of 128 Hz +/-5 percent and a duty cycle of 25-95 percent is a valid delivered torque signal. The percentage of duty cycle is proportionate to the percentage of delivered engine torque.

DTC Descriptor


DTC C0244 Pulse Width Modulated (PWM) Delivered Torque



� The engine is running.


� The EBTCM does not receive the delivered torque signal (open or shorted circuit).

� An incorrect delivered torque signal is detected by the EBTCM.


Traction control will be disabled.

Diagnostic Aids


� If an intermittent malfunction exists, refer to Checking Aftermarket Accessories in Wiring Systems.

� Possible causes for DTC C0244 to set:

� Open in the torque delivered control circuit

� Torque delivered control circuit shorted to ground or voltage

� Communication frequency problem

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� Communication duty cycle problem

� Torque delivered control circuit has a wiring problem, terminal corrosion, or poor connections

� EBCM not receiving information from the ECM

Test Description


3: This step tests for voltage supplied to the ECM from the EBCM.

4: This step tests for a shorted resistor in the EBCM or a short to voltage within the circuit, by verifying that a large voltage drop occurs in the circuit when the test lamp is placed in parallel with the DMM. The ECM may be damaged if either of these conditions is present.

DTC C0244 Step Action Values Yes No


1


-

Go to Step 2

Go to Diagnostic



2




Does the DTC set?

-

Go to Step 3 Go to

Diagnostic Aids

3

Use the scan tool in order to monitor the delivered engine torque in the ABS data display. Does the scan tool show a delivered engine torque value between 90-100 percent?

-Go to

Diagnostic Aids Go to Step 4

4

Test the delivered torque signal circuit for an open or a short. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?

-

- Go to Step 5

5

1. Disconnect the electronic brake and traction control module (EBTCM).

2. Using a DMM measure the voltage on the delivered torque signal circuit.

Does the voltage measured equal the specified value?

B+


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DTC C0245

6


2. Inspect for poor connections at the harness connector of the electronic brake control module (EBCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

-


7

Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?

-

Go to Step 10 -

8

Inspect for poor connections at the harness connector of the Engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?

-


9

Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?

-

Go to Step 10 -

10





Does the DTC reset?

-


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Fig. 11: Wheel Speed Sensors Wiring Schematic Courtesy of GENERAL MOTORS CORP.

Circuit Description

Antilock brake system (ABS) equipped vehicles have wheel speed sensors (WSSs) at all 4 wheels. The front WSSs monitor the speed of each wheel by placing a magnetic coupling next to a toothed ring mounted on the

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axle of each wheel. The rear WSSs monitor speed of each wheel with a magnetic coupling and a toothed ring internal to the wheel bearings. These sensors produce an AC signal that the electronic brake traction control module (EBTCM) uses to calculate the wheel speed. The signal frequency changes with the wheel speed. DTC C0245 will set when the EBTCM cannot specifically identify which WSS is causing the malfunction. DTC C0245 will be in history and the DTC associated with the malfunctioning sensor will be set along with DTC C0245.

DTC Descriptor


DTC C0245 Wheel Speed Sensor Frequency Error


� The ignition switch is ON.

� The DTC can be set after system initialization.


DTC C0245 will set if the following conditions exist:

� The EBTCM detects a deviation between the left and the right rear wheel speeds of greater than 6 km/h (3.75 mph) at a vehicle speed of less than 100 km/h (62 mph) on vehicles equipped with traction control system (TCS).

� The EBTCM detects a deviation between the left and the right front wheel speeds of greater than 10 km/h (6.25 mph) at a vehicle speed of less than 100 km/h (62 mph).

� The EBTCM detects a deviation between the left and the right rear wheel speeds of greater than 6 percent of the vehicle speed at greater than 100 km/h (62 mph) on vehicles equipped with TCS.

� The EBTCM detects a deviation between the left and the right front wheel speeds of greater than 4 km/h plus 6 percent of the vehicle speed at greater than 100 km/h (62 mph).

� When this DTC sets, the traction control and the dynamic rear proportioning (DRP) turn ON the antilock telltale.


� The EBTCM disables the ABS/TCS/DRP.



� The condition for the DTC is no longer present and the DTC is cleared with a scan tool.

� The EBTCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids

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� It is very important to thoroughly inspect the wiring components and the connectors. Failure to carefully and fully inspect the wiring and the connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.

� Inspect any circuitry that may be causing the complaint for the following conditions:


� Improper mating









� Possible causes for DTC C0245 to set:

� Damaged or missing teeth on one or more of the WSS rings

� Large grooves or gouges, or buildup of foreign material in the gaps between the WSS ring teeth

� A worn front hub bearing assembly, or a worn inner axle bearing which allows the sensor to toothed ring gap to change excessively

Test Description

The numbers below refer to step numbers on the diagnostic table.

2: If DTC C0245 is a history code, this step checks if a specific wheel speed circuit malfunction DTC is set concurrently with DTC C0245.

5: This step checks if the WSS harness is routed in close proximity to the spark plug wires.

7: In this step, if the scan tool can record any erroneous WSS signals, diagnose that sensors first.



1


Go to Step 2



2

Are any of the following DTCs set concurrently with a history DTC C0245?

� DTC C0035 Go to Diagnostic Trouble Code

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� DTC C0040

� DTC C0045

� DTC C0050

(DTC) List - Vehicle in Vehicle DTC Information Go to Step 3

3Inspect the wheel speed sensor (WSS) for physical damage. Is physical damage of the WSS evident? Go to Step 4 Go to Step 5

4

Replace the WSS. Refer to Wheel Speed Sensor Replacement - Front or Wheel Speed Sensor Replacement - Rear. Is the replacement complete? Go to Step 12 -

5

Check for proper routing of the WSS harness. Check that the WSS harness is routed away from the spark plug wires. Is the WSS harness properly routed? Go to Step 7 Go to Step 6

6Reroute the WSS harness away from the spark plug wires. Is the reroute complete? Go to Step 12 -

7

1. Reconnect all previously disconnected components.


3. Turn the ignition switch to the RUN position.

4. Set the scan tool to Snap Shot Auto Trigger mode and monitor the wheel speed sensors.

5. Carefully drive the vehicle above 40 km/h (25 mph) for several minutes.

Did the scan tool trigger on any of the wheel speed sensors? Go to Step 8 Go to Step 9

8

Note which wheel speed sensor triggered the scan tool. Follow the appropriate wheel speed sensor malfunction DTC table for the wheel speed sensor that triggered. Refer to DTC Table. Is the repair complete? Go to Step 12 -

9

1. Using a scan tool, clear the DTC.

2. Remove the scan tool from the data link connector (DLC).

3. Carefully drive the vehicle above 40 km/h (25 mph) for several minutes.

Does the DTC reset as a current DTC? Go to Step 11 Go to Step 10 Malfunction is intermittent. Inspect all connectors and harnesses for damage that may result in an open or high resistance when connected. Refer to Testing for

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DTC C0550

Circuit Description

The electronic brake control module (EBCM) performs several self-tests for internal problems which may affect proper operation.

DTC Descriptor


DTC C0550 Electronic Control Unit (ECU)


The ignition is ON.


The EBCM detects an internal malfunction.


� The EBCM disables the antilock brake system/dynamic rear proportion (DRP)/traction control system (TCS).




Certain conditions that may cause this DTC to set cannot be cleared. Other conditions that may cause this DTC

10Intermittent Conditions and Poor Connections in Wiring Systems. Is the repair complete? Go to Step 12 -

11

Replace the electronic brake control module (EBCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Is the replacement complete? Go to Step 12 -

12




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to set may be cleared, at least temporarily, by using the scan tool Clear DTCs function.

Diagnostic Aids

Replace the EBCM if this DTC continues to set intermittently.

DTC C0550

DTC C0551

Step Action Yes No

1


Go to Step 2



2 Use a scan tool in order to clear the DTCs. Can the DTC be cleared? Go to Step 3 Go to Step 4

3




Aids

4


5






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Fig. 12: Identifying ABS Control Module Courtesy of GENERAL MOTORS CORP.

DTC Descriptor


DTC C0551 Option Configuration Error


DTC C0551 will set if the ABS control module option configuration bit does not match the vehicle.

When DTC C0551 sets:

� The TRAC switch LED is commanded OFF.

� The ABS control module will disable the traction control system (TCS).

Diagnostic Aids

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DTC C0896


Circuit Description

The electronic brake control module (EBCM) is required to operate within a specified range of voltage to function properly. During antilock brake system (ABS) and traction control system (TCS) operation, there are current requirements that will cause the voltage to drop. Because of this, voltage is monitored out of ABS/TCS control to indicate a good charging system condition, and also during ABS/TCS control when voltage may drop significantly. The EBCM also monitors for high voltage conditions which could damage the EBCM.

DTC Descriptor


DTC C0896 System High/Low Voltage

IMPORTANT: When C0551 sets, the TCS is disabled for the entire ignition cycle.

IMPORTANT: New ABS control modules will automatically set DTC C0551 when installed. To clear DTC C0551, new modules must be configured with the correct engine and transmission option bit. Refer to ABS Programming on the scan tool.

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The vehicle speed is above 6.4 km/h (4 mph).


The battery voltage drops below 9.4 volts or exceeds 17.4 volts.


� The ABS telltale will be turned ON.

� The ABS control module will disable the ABS, the TCS, and the dynamic rear proportion (DRP).


The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Diagnostic Aids

Use the scan tool to observe the battery voltage display.

DTC C0896

IMPORTANT: If the battery voltage returns to normal levels 9.4-17.4 volts within the same ignition cycle, the ABS control module will enable ABS/TCS/DRP and will turn the ABS telltale OFF.

Step Action Values Yes NoSchematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views

1


-

Go to Step 2

Go to Diagnostic



2




Does the DTC set?

-

Go to Step 3 Go to

Diagnostic Aids

3

1. With the engine running, turn ON all accessories.

2. Use the scan tool in order to monitor the battery voltage in the ABS data display.

12.6 V

Go to

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SYMPTOMS - ANTILOCK BRAKE SYSTEM

Visual/Physical Inspection

� Inspect for aftermarket devices which could affect the operation of the antilock brake system. Refer to Checking Aftermarket Accessories in Wiring Systems.

� Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

� Inspect the master cylinder reservoir for the proper fluid level.

Intermittent

Is the battery voltage below the specified value? Go to Step 4 Diagnostic Aids

4Using the scan tool, monitor the battery voltage in the engine control module (ECM) data list. Is the battery voltage below the specified value?

12.6 V Go to Charging system Go to Step 5

5

Test the battery positive voltage circuits for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?

-


6

Replace the electronic brake control module (EBCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?

-

Go to Step 7 -

7

1. Use the scan tool to clear the DTC.




Does the DTC reset?

-


IMPORTANT: The following steps must be completed before using the symptom tables.

1. Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information, before using the Symptom Tables in order to verify that all of the following are true:

� There are no DTCs set. � The control modules can communicate via the serial data link.

2. Review the system operation in order to familiarize yourself with the system functions. Refer to ABS Description and Operation.

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Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

� ABS Indicator Always On

� ABS Indicator Inoperative

� Low Traction Indicator Always On

� Low Traction Indicator Inoperative

� Traction Control Indicator Always On

� Traction Control Indicator Inoperative

ABS INDICATOR ALWAYS ON

Circuit Description

The instrument panel cluster (IPC) turns the ABS indicator ON during the IPC bulb check for approximately 3 seconds when the ignition switch is turned to the ON position. If the electronic brake control module (EBCM) sets a DTC, the EBCM sends a class 2 message to the IPC to command the ABS indicator ON.

Diagnostic Aids




� Improper mating

� Broken locks








� If an intermittent malfunction exists, refer to Inducing Intermittent Fault Conditions in Wiring Systems.

Test Description

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2: This step verifies that the scan tool can turn ON and OFF all the indicator lamps in the instrument cluster.

4: This step verifies that the circuits going to the instrument cluster or the cluster is at fault.

ABS Indicator Always On

ABS INDICATOR INOPERATIVE

Step Action Yes NoSchematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views or Instrument Panel, Gages, and Console Connector End Views in Instrument Panel, Gages, and Console

1


Go to Step 2



2

1. Using a scan tool, select the Instrument Panel Cluster Special Functions mode.

2. Select Lamp Test.

3. In the Lamp Test mode you can turn ON or OFF the instrument panel indicators. All indicators will turn ON when commanded ON.

Does the ABS indicator turn ON then OFF? Go to Step 3 Go to Step 4

3

Replace the electronic brake control module (EBCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Is the replacement complete?


Vehicle in Vehicle DTC Information -

4

1. Disconnect the instrument cluster and connect a test light across the appropriate power and ground terminals.

2. With the test light OFF, repair the open in the power or ground circuit to cluster.

3. With the test light ON, verify the connector for a poor connection to the cluster.

4. If OK, replace the instrument cluster. Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console.

Is the instrument cluster replacement complete?



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Circuit Description

The instrument panel cluster (IPC) turns the ABS indicator ON during the IPC bulb check for approximately 3 seconds when the ignition switch is turned to the ON position. If the electronic brake control module (EBCM) sets a DTC, the EBCM sends a class 2 message to the IPC to command the ABS indicator ON.

Diagnostic Aids




� Improper mating

� Broken locks








� If an intermittent malfunction exists, refer to Inducing Intermittent Fault Conditions in Wiring Systems.

Test Description




ABS Indicator Inoperative Step Action Yes No

Schematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views or Instrument Panel, Gages, and Console Connector End Views in Instrument Panel, Gages, and Console

1


Go to Step 2



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LOW TRACTION INDICATOR ALWAYS ON

Circuit Description

The instrument panel cluster (IPC) turns the LOW TRAC indicator ON during the IPC bulb check for approximately 3 seconds when the ignition switch is turned to the ON position. If the electronic brake control module (EBCM) sets a DTC, the EBCM sends the IPC the command to turn the LOW TRAC indicator ON.

Diagnostic Aids




� Improper mating

� Broken locks


2


2. Select the Lamp Test.


Does the ABS indicator turn ON then OFF? Go to Step 3 Go to Step 4

3




4



3. With the test light ON, check the connector for a poor connection to cluster.





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� If an intermittent malfunction exists, refer to Inducing Intermittent Fault Conditions in Wiring Systems for further diagnosis.

Test Description




Low Traction Indicator Always On Step Action Yes No

Schematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views or Instrument Panel, Gages, and Console Connector End Views in Instrument Panel, Gages, and Console

1


Go to Step 2



2


2. Select the Lamp Test.


Does the LOW TRAC indicator turn ON then OFF? Go to Step 3 Go to Step 4

3





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LOW TRACTION INDICATOR INOPERATIVE

Circuit Description

The instrument panel cluster (IPC) turns the LOW TRAC indicator ON during the IPC bulb check for approximately 3 seconds when the ignition switch is turned to the ON position. If the electronic brake control module (EBCM) sets a DTC, the EBCM sends the IPC the command to turn the LOW TRAC indicator ON.

Diagnostic Aids




� Improper mating

� Broken locks








� If an intermittent malfunction exists, refer to Inducing Intermittent Fault Conditions in Wiring System for further diagnosis.

Test Description



4


3. With the test light ON, check the connector for a poor connection to cluster.





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Low Traction Indicator Inoperative

TRACTION CONTROL INDICATOR ALWAYS ON

Circuit Description

The TRAC OFF indicator is controlled by the instrument cluster via class 2 serial data messages from the electronic brake control module (EBCM). When the body control module (BCM) sees the traction control switch input grounded through the momentary traction control switch, it sends a class 2 message to the EBCM

Step Action Yes NoSchematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views or Instrument Panel, Gages, and Console Connector End Views in Instrument Panel, Gages, and Console

1


Go to Step 2



2


2. Select the Lamp Test in Output Control.


Does the LOW TRAC indicator turn ON then OFF? Go to Step 3 Go to Step 4

3




4



3. With the test light ON, check the connector for a poor connection to the cluster.





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that tells the EBCM that the traction control switch has been pressed. The EBCM then disables traction control and sends a message to the instrument cluster to turn the TRAC OFF indicator ON. Each time the ignition is cycled from OFF to ON, the traction control system (TCS) is enabled.

The following conditions will cause the TRAC OFF indicator to illuminate:

� The EBCM has disabled the TCS due to a DTC.

� The driver manually disabling the TCS via the traction control switch

� The instrument cluster bulb check-When the ignition switch is turned to ON, the TRAC OFF indicator will turn ON for approximately 3 seconds and then turn OFF.

Diagnostic Aids




� Improper mating

� Broken locks








� If an intermittent malfunction exists, refer Inducing Intermittent Fault Conditions in Wiring Systems for further diagnosis.

Traction Control Indicator Always On Step Action Yes No

Schematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views or Computer/Integrating Systems Connector End Views in Computer/Integrating System

1


Go to Step 2





3. With a scan tool, observe the Traction Switch

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2

parameter in the body control module (BCM) data display, Inputs.

4. Activate the traction control switch.

Does the Traction Switch parameter change state?

Go to Testing for Intermittent

Conditions and Poor Connections in Wiring Systems Go to Step 3

3


2. Disconnect the traction control switch connector.

3. Connect a fused jumper from the signal circuit of the traction control switch harness connector to a good ground.


5. With a scan tool, observe the Traction Switch parameter.

Does the scan tool display Active? Go to Step 5 Go to Step 4

4

Test the signal circuit of the traction control switch for an open or high resistance. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 10 Go to Step 6

5

Test the ground circuit of the traction control switch for an open or high resistance. Refer to Testing for Continuity in Wiring Systems. Did you find and correct the condition? Go to Step 10 Go to Step 7

6

Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 10 Go to Step 8

7

Inspect for poor connections at the harness connector of the traction control switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 10 Go to Step 9

8

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? Go to Step 10 -

9

Replace the traction control switch. Refer to Traction Control Switch Replacement in Steering Wheel and Column. Did you complete the replacement? Go to Step 10 -

10Operate the system in order to verify the repair. Did you correct the condition? System OK Go to Step 2

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TRACTION CONTROL INDICATOR INOPERATIVE

Circuit Description

The TRAC OFF indicator is controlled by the instrument cluster via class 2 serial data messages from the electronic brake control module (EBCM). When the body control module (BCM) sees the traction control switch input grounded through the momentary traction control switch, it sends a class 2 message to the EBCM that tells the EBCM that the traction control switch has been pressed. The EBCM then disables traction control and sends a message to the instrument cluster to turn the TRAC OFF indicator ON. Each time the ignition is cycled from OFF to ON, the traction control system (TCS) is enabled.

The following conditions will cause the TRAC OFF indicator to illuminate:

� The EBCM has disabled the TCS due to a DTC.

� The driver manually disabling the TCS via the traction control switch

� The instrument cluster bulb check-When the ignition switch is turned to ON, the TRAC OFF indicator will turn ON for approximately 3 seconds and then turn OFF.

Diagnostic Aids




� Improper mating

� Broken locks








� If an intermittent malfunction exists, refer to Inducing Intermittent Fault Conditions in Wiring Systems for further diagnosis.

Traction Control Indicator Inoperative Step Action Yes No

Schematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views or Computer/Integrating Systems Connector End Views in Computer/Integrating System

Did you perform the Diagnostic System Check - Go to Diagnostic

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1Vehicle?

Go to Step 2

System Check - Vehicle in Vehicle DTC Information

2



3. With a scan tool, observe the Traction Switch parameter in the body control module (BCM) data display, Inputs.

Does the scan tool display Inactive? Go to Step 3 Go to Step 4

3

1. Activate the traction control switch.

2. With the scan tool, observe the Traction Switch parameter.

Does the Traction Switch parameter change state?

Go to Testing for Intermittent

Conditions and Poor Connections in Wiring Systems Go to Step 4

4


2. Disconnect the traction control switch connector.


4. With a scan tool, observe the Traction Switch parameter.

Does the scan tool display Inactive? Go to Step 7 Go to Step 5

5

Test the signal circuit of the traction control switch for a short to ground. Refer to Testing for Short to Ground in Wiring Systems. Did you find and correct the condition? Go to Step 10 Go to Step 6

6

Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 10 Go to Step 8

7

Inspect for poor connections at the harness connector of the traction control switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? Go to Step 10 Go to Step 9

8

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? Go to Step 10 -

9Replace the traction control switch. Refer to Traction Control Switch Replacement. Did you complete the replacement? Go to Step 10 -

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REPAIR INSTRUCTIONS

ABS AUTOMATED BLEED PROCEDURE

The ABS Automated Bleed Procedure uses a scan tool to cycle the system solenoid valves and run the pump in order to purge any air from the secondary circuits. These circuits are normally closed off, and are only opened during system initialization at vehicle start-up and during ABS operation. The automated bleed procedure opens these secondary circuits and allows any air trapped in these circuits to flow out toward the brake corners.

Performing the Automated Bleed Procedure


2. Remove all 4 tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.

3. Inspect the brake system for leaks and visual damage. Refer to Symptoms - Hydraulic Brakes in

10 Operate the system in order to verify the repair. Did you correct the condition? System OK Go to Step 2

CAUTION: Refer to Brake Fluid Irritant Caution in Cautions and Notices.

NOTE: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

IMPORTANT: Before performing the ABS Automated Bleed Procedure, first perform a manual or pressure bleed of the base brake system. Refer to Hydraulic Brake System Bleeding (Manual) or Hydraulic Brake System Bleeding (Pressure) in Hydraulic Brakes. The automated bleed procedure is recommended when one of the following conditions exist:

� Base brake system bleeding does not achieve the desired pedal height or feel.

� Extreme loss of brake fluid has occurred. � Air ingestion is suspected in the secondary circuits of the brake

modulator assembly.

NOTE: The Auto Bleed Procedure may be terminated at any time during the process by pressing the EXIT button. No further Scan Tool prompts pertaining to the Auto Bleed procedure will be given. After exiting the bleed procedure, relieve bleed pressure and disconnect bleed equipment per manufacturers instructions. Failure to properly relieve pressure may result in spilled brake fluid causing damage to components and painted surfaces.

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Hydraulic Brakes. Repair or replace components as needed.

4. Lower the vehicle.

5. Inspect the battery state of charge. Refer to Battery Inspection/Test in Engine Electrical.


7. Turn the ignition ON, with the engine OFF.

8. With the scan tool, establish communications with the ABS system. Select Special Functions. Select Automated Bleed from the Special Functions menu.


10. Following the directions given on the scan tool, pressure bleed the base brake system. Refer to Hydraulic Brake System Bleeding (Manual) or Hydraulic Brake System Bleeding (Pressure) in Hydraulic Brakes.

11. Follow the scan tool directions until the desired brake pedal height is achieved.

12. If the bleed procedure is aborted, a malfunction exists. Perform the following steps before resuming the bleed procedure:

� If a DTC is detected, refer to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information and diagnose the appropriate DTC.

� If the brake pedal feels spongy, perform the conventional brake bleed procedure again. Refer to Hydraulic Brake System Bleeding (Manual) Hydraulic Brake System Bleeding (Pressure) in Hydraulic Brakes.

13. When the desired pedal height is achieved, press the brake pedal to inspect for firmness.


15. Remove the scan tool.

16. Install the tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.

17. Inspect the brake fluid level. Refer to Master Cylinder Reservoir Filling in Hydraulic Brakes.

18. Road test the vehicle while inspecting that the pedal remains high and firm.

ELECTRONIC BRAKE CONTROL MODULE REPLACEMENT

Removal Procedure



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Fig. 14: Disconnecting Brake Pipe Nuts From Brake Pressure Modulator Valve Courtesy of GENERAL MOTORS CORP.

1. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical.

2. Disconnect the brake pipe nuts from the brake pressure modulator valve (BPMV).

IMPORTANT: Plug open brake pipes to prevent brake fluid loss and contamination.

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Fig. 15: Removing & Installing Brake Pipe-To-Master Cylinder Nuts Courtesy of GENERAL MOTORS CORP.

3. Disconnect the brake pipe nuts from the master cylinder.

4. Slide out the locking tab and disconnect the electronic brake and traction control module (EBCM) electrical connector.

IMPORTANT: After removing brake pipe nuts, do not excessively pull or bend brake pipes away from master cylinder.


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5. Remove the ABS control module mounting nuts and the bracket.

6. Remove the ABS control module from the vehicle.

Assembly Procedure

1. Disconnect the pump motor electrical connector.

2. Remove the EBCM to BPMV screws.

3. Separate the EBCM from the BPMV.

4. Position the EBCM on the BPMV.

5. Install the attaching screws.

6. Connect the pump motor electrical connector.

Installation Procedure

IMPORTANT: Do not bend brake pipes.

IMPORTANT: Do not attempt to repair a damaged solenoid pack or control unit assemblies. Repair of these assemblies is not possible. Do not lubricate or oil the EBCM.

NOTE: Refer to Fastener Notice in Cautions and Notices.

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Fig. 16: Positioning ABS Control Assembly In Bracket Courtesy of GENERAL MOTORS CORP.

1. Position the ABS control assembly into the bracket and tighten the nuts.

Tighten: Tighten the ABS control assembly-to-bracket nuts to 20 N.m (15 lb ft).

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2. Position the brake pipes into the master cylinder and tighten the brake pipe nuts.

Tighten: Tighten the brake pipes-to-master cylinder to 18 N.m (13 lb ft).

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3. Position the brake pipes into the ABS control assembly and tighten the brake pipe nuts.


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Fig. 19: Installing ABS Control Assembly Electrical Connector Courtesy of GENERAL MOTORS CORP.

4. Install the electrical connector to the ABS control assembly.

5. Install the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure in

IMPORTANT: Ensure that all the electrical connections are fully seated and the latches are engaged.

IMPORTANT: If the EBCM was replaced, make sure to program the correct engine and transaxle options in the EBCM. Refer to option bit configuration with scan tools.

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Engine Electrical.

6. Fill the brake fluid reservoir with clean brake fluid up to the "MAX" mark on the reservoir.

7. Bleed the brakes. Refer to Hydraulic Brake System Bleeding (Manual) or Hydraulic Brake System Bleeding (Pressure) in Hydraulic Brakes.

BRAKE PRESSURE MODULATOR VALVE (BPMV) REPLACEMENT

Removal Procedure

IMPORTANT: It is not required or recommended to bleed the ABS controller. Automated bleeding of the ABS controller may induce air into the system.



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6. Remove the ABS control module from the vehicle.

Assembly Procedure

1. Disconnect the pump motor electrical connector.

2. Remove the EBCM to BPMV screws.

3. Separate the EBCM from the BPMV.

4. Position the EBCM on the BPMV.

5. Install the attaching screws.

6. Connect the pump motor electrical connector.



IMPORTANT: Do not attempt to repair a damaged solenoid pack or control unit assemblies. Repair of these assemblies is not possible. Do not lubricate or oil the EBCM.


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IMPORTANT: If the EBCM was replaced, make sure to program the correct engine and transaxle options in the EBCM. Refer to option bit configuration with scan tools.

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Engine Electrical.



BRAKE PRESSURE MODULATOR VALVE (BPMV) BRACKET REPLACEMENT

Removal Procedure


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IMPORTANT: If the EBCM was replaced, make sure to program the correct engine and transaxle options in the EBCM. Refer to option bit configuration with Scan tools.

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Engine Electrical.



WHEEL SPEED SENSOR REPLACEMENT - FRONT

Removal Procedure


CAUTION: Ensure that the vehicle is properly supported and squarely positioned. To help avoid personal injury when a vehicle is on a hoist, provide additional support for the vehicle on the opposite end from which the components are being removed.

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Fig. 33: Locating Front Wheel Speed Sensor Electrical Connector Courtesy of GENERAL MOTORS CORP.

1. Raise the vehicle on a hoist.

2. Remove the rear wheel and the tire assembly. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.

3. Disconnect the wheel speed sensor electrical connector.

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Fig. 34: Removing & Installing Front Wheel Speed Sensor Courtesy of GENERAL MOTORS CORP.

4. Remove the wheel speed sensor to bracket TORX® head bolt.

5. Remove the wheel speed sensor.

NOTE: The outer drive axle joint has a speed sensor ring. Be careful not to damage this ring when performing service operations near knuckle and drive axle. Never pry against the speed sensor ring. Even minor scratching of speed sensor ring may result in a loss of ABS operation.

NOTE: Wheel speed sensor bracket uses a locating pin on the steering knuckle.

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6. Remove the wheel speed sensor bracket to the steering knuckle bolt.


Fig. 35: Removing & Installing Front Wheel Speed Sensor Courtesy of GENERAL MOTORS CORP.

1. Position the wheel speed sensor bracket into the steering knuckle and install the fastener.

Be careful not to break the pin when removing the bracket.


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Tighten: Tighten the wheel speed sensor bracket-to-steering knuckle to 8 N.m (71 lb in).

2. Install the wheel speed sensor into the bracket.

Tighten: Tighten the wheel speed sensor bracket-to-steering sensor bracket to 8 N.m (71 lb in).

3. Connect the wheel speed sensor electrical connector.

4. Install the wheel and the tire assemblies onto the hub. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.

WHEEL SPEED SENSOR REPLACEMENT - REAR

Removal Procedure

1. Raise and support the vehicle on a suitable hoist. Refer to Lifting and Jacking the Vehicle in General Information.

2. Remove the rear tire and wheel assembly. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.

NOTE: Before installing wheels, remove rust or corrosion from wheel mounting surfaces and brake rotors/drums. Failure to do so can cause wheel nuts to loosen in service.

IMPORTANT: The rear wheel speed sensors and rings are integral with the hub and bearing assemblies. If a speed sensor or a ring needs replacement, replace the entire hub and bearing assembly. Refer to Wheel Bearing/Hub Replacement - Rear in Rear Suspension.

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Fig. 36: Locating Rear Wheel Speed Sensor Electrical Connector Courtesy of GENERAL MOTORS CORP.

3. Disconnect the electrical connector from the rear wheel speed sensor.

4. Remove the hub and bearing assembly. Refer to Wheel Bearing/Hub Replacement - Rear in Rear Suspension.


1. Install the hub and bearing assembly to the vehicle. Refer to Wheel Bearing/Hub Replacement - Rear in Rear Suspension.

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Fig. 37: Locating Rear Wheel Speed Sensor Electrical Connector Courtesy of GENERAL MOTORS CORP.

2. Connect the electrical connector to the rear wheel speed sensor.

3. Install the wheel and tire assembly. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.


5. Turn the ignition switch to the ON position, with the engine OFF.

6. Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information.

TRACTION CONTROL SWITCH REPLACEMENT

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Removal Procedure

Fig. 38: Removing & Installing Instrument Panel Center Trim Plate Courtesy of GENERAL MOTORS CORP.

1. Remove the center trim plate by gently pulling rearward at the top to disengage the retaining clips.

2. Tilt the trim plate sideways and disconnect the traction control switch electrical connector.

3. Release the traction control switch lock tabs and push the switch through the front of the center trim plate.


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Fig. 39: Removing & Installing Instrument Panel Center Trim Plate Courtesy of GENERAL MOTORS CORP.

1. Push the traction through the front of the center trim plate until the switch snaps into the lock tabs.

2. Connect the traction control switch electrical connector.

3. Push the center trim plate into the instrument panel to engage the retaining clips.

DESCRIPTION AND OPERATION

ABS DESCRIPTION AND OPERATION

The purpose of the ABS is to minimize wheel slip during heavy braking. The ABS performs this function by

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monitoring the speed of each wheel and controlling the brake fluid pressure to each wheel independently during a braking event. This allows the driver to maintain directional stability while minimizing stopping distance.

Valve Assembly (BPMV)

The valve assembly provides brake fluid pressure modulation for each of the individual wheel circuits, as required, during an ABS/traction control system (TCS) event. During an ABS event, the valve assembly can maintain or reduce brake fluid pressure that is applied by the master cylinder. The valve assembly cannot increase pressure beyond what is applied by the master cylinder (driver). The valve assembly contains a motor-driven pump, ABS inlet and outlet valves, as well as TCS prime and isolation valves. With exception of the ABS control module, the valve assembly is not serviceable and should never be disassembled.

The valve assembly is an addition to the 4-circuit diagonally-split hydraulic system found on vehicles without ABS.

ABS Control Module (EBTCM)

The ABS control module monitors the speed of each wheel to detect wheel slip. If wheel slip is detected, the module commands the appropriate valve positions in the valve assembly to modulate brake pressure in some or all of the hydraulic circuits. This action prevents wheel slip and provides optimum braking. In addition, the ABS control module performs a continuous diagnostic routine to detect malfunctions. If the module detects an electrical malfunction, it can disable ABS/traction control module (TCS)/dynamic rear positioning (DRP), illuminate the appropriate telltale and store a DTC.

The ABS control module contains a solenoid for each ABS/TCS valve it operates and a relay for the solenoid circuit and pump motor circuit respectively. The relays and solenoids are not serviceable.

ABS Operation

During an ABS event, the ABS control module will control the hydraulic pressure in the individual wheel circuits to prevent any wheel from slipping. The control module can decrease or hold hydraulic pressure by energizing the appropriate valve solenoid. A rapid pulsation is felt in the brake pedal and a ticking or popping noise can be heard as control module commands valve solenoids in response to wheel speed changes.

When the ABS control module detects wheel slip, it holds pressure by closing both the inlet valve from the master cylinder and the outlet valve. If pressure hold is not enough to control wheel slip, the ABS control module releases pressure by opening the outlet valve and allowing some pressure bleed-off into the accumulator. The accumulator stores this fluid until the motor-driven pump returns fluid to the master cylinder.

The control module opens the inlet valve to allow master cylinder pressure to the wheel circuits again when no wheel slip is detected.

Traction Control System (TCS)

The traction control system (TCS) compares front-wheel speeds to rear-wheel speeds to determine if drive wheels lose traction. The TCS activates when drive wheel speed exceeds speed of non-drive wheels by a calibrated value. This allows the driver to maintain acceleration and directional stability while accelerating on low traction surfaces.

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The TCS limits wheel slip during acceleration when one or more of the drive wheels lose traction. The brake switch must be OFF for TCS to operate.

The ABS control module monitors wheel speed output and compares drive wheel to non-drive wheel values to detect wheel slip. During a TCS event, the ABS control module sends a requested torque value to the engine control module (ECM). The ECM initiates an engine torque reduction routine to slow down the drive wheels. This routine consists of ignition timing reduction, fuel injector cut-off and transmission shift control. The ECM also sends a torque delivered value to the ABS control module. If the engine management routine is insufficient to achieve the desired wheel speed, the ABS control module will then use the TCS isolation valves and prime valves to slow down the drive wheels. The isolation valves close to isolate the wheel circuit from the master cylinder and the prime valves open to allow the motor-driven pump to access master cylinder fluid so it can build pressure to apply the desired brake.

If the ABS control module detects a malfunction, it will disable TCS and will command the body control module (BCM) to turn the TRAC LED OFF. The driver can also disable TCS, if desired, by depressing the TRAC switch. When the driver depresses the TRAC switch, the ABS control module will disable TCS and will command the BCM to turn the TRAC LED OFF.

Dynamic Rear Proportioning (DRP)

Dynamic rear proportioning (DRP) is an electronic brake proportioning feature that replaces the mechanical proportioning valve in the base brake system. DRP uses existing ABS components to regulate the vehicle rear brake pressure and provide optimum front-rear brake balance in all braking situations.

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2005 antilock brakes

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