Vehicle Dynamic Suspension -...

Vehicle Dynamic Suspension

Refer to Wiring Diagrams Cell 41, Rear Air Suspension for schematic and connector information.

Principles of Operation

WARNING: Before repairing or installing any air suspension component(s), turn off the air suspension switch or disconnect the battery ground cable to prevent vehicle damage or personal injury.

WARNING: Do not attempt to install or inflate any air spring that has become unfolded to prevent vehicle damage or personal injury.

WARNING: Failure to observe the following procedures may result in a sudden failure of the suspension system.

WARNING: Any air spring which is unfolded must be refolded prior to being installed in a vehicle.

WARNING: The air spring refolding procedure should not be used for an air spring which has never supported the vehicle's weight while in the correctly folded position.

WARNING: Vehicles with an incorrectly folded air spring(s) found after the vehicle has been driven, must have a new air spring installed.

WARNING: Do not attempt to inflate any air spring which has collapsed while deflated from the rebound hanging position to the jounce stop.

WARNING: When installing a new air spring, care must be taken to not apply a load to the suspension until the air springs have been inflated using the air spring fill procedure.

WARNING: After inflating an air spring in the hanging position, it must be inspected for proper shape.

The air suspension system is designed to improve ride handling and general vehicle driving performance.

Rear Air Suspension Control Module

A microprocessor controls the air suspension system. The microprocessor and its supporting hardware are contained in the rear air suspension control module. The rear air suspension control module responds to signals from various sensors in the vehicle to maintain the programmed ride height while the vehicle is either moving or stopped. The rear air suspension control module accomplishes this by opening and closing solenoid valves to control the amount of air in the air spring(s). The rear air suspension control module turns on the compressor by applying voltage through the compressor relay to inflate the air spring(s) and raise the vehicle. The rear air suspension control module opens the vent solenoid to lower the vehicle by releasing air from the air spring(s) in response to signal inputs from the air suspension height sensor(s).

Air Suspension Switch

CAUTION: The air suspension switch must be turned to the OFF position when the vehicle is hoisted, jacked, towed, jump started, or raised off the ground, to avoid unnecessary operation of the system and possible damage to the air suspension system components.

The air suspension switch provides a signal to the rear air suspension control module in the ON position to activate the system to maintain the programmed vehicle height.

Air Compressor

NOTE: The compressor contains a thermal overload circuit breaker. The circuit breaker automatically resets after a cool down period and after being tripped by excessive compressor motor heat.

The air compressor assembly consists of the compressor pump, electric motor and vent solenoid (must be installed as an assembly).

Air Suspension Height Sensor

The air suspension height sensor sends signals to the air suspension control module. There are three possible conditions that the air suspension control module interprets from the signals of the air suspension height sensors. The conditions are trim height, below trim height, or above trim height.

Solenoid Valve, Air Spring

SECTION 204-05: Vehicle Dynamic Suspension 2000 Town Car Workshop Manual

DIAGNOSIS AND TESTING Procedure revision date: 05/27/1999

Special Tool(s)

Worldwide Diagnostic System (WDS) 418-F224 New Generation STAR (NGS) Tester 418-F052 or equivalent scan tool

Vacuum Tester or equivalent 014-R1054

73 Digital Multimeter or equivalent 105-R0051

of 302000 Town Car Workshop Manual

9/23/2010http://www.fordtechservice.dealerconnection.com/pubs/content/~WSYG/~MUS~LEN/19/...

WARNING: Never rotate an air spring solenoid valve to the release slot in the air spring end cap fitting until all pressurized air has escaped from the air spring to prevent vehicle damage or personal injury.

The air spring solenoid valve allows air to enter and exit the rear air springs during height adjustment operations. The air spring solenoid valve is electrically operated and controlled by the air suspension control module.

Steering Sensor

The steering sensor provides the steering rate and position to the air suspension control module to avoid overcompensation of the air suspension during turns.

Inspection and Verification

1. Verify the customer concern.

2. NOTE: If the door ajar indicator is illuminated, repair the door ajar indicator. For additional information, refer to Section 413-09.

Visually inspect for obvious signs of mechanical and electrical damage.

Visual Inspection Chart

3. If the concern remains after the inspection, connect scan tool to the data link connector (DLC) located beneath the instrument panel and select the vehicle to be tested from the scan

tool menu. If scan tool does not communicate with the vehicle:

� check that the program card is properly installed.

� check the connections to the vehicle.

� check the ignition switch position.

4. If the scan tool still does not communicate with the vehicle, refer to the scan tool manual.

5. Carry out the DATA LINK DIAGNOSTIC TEST. If scan tool responds with:

� CKT914, CKT915 or CKT70 = ALL ECUS NO RESP/NOT EQUIP. Refer to Section 418-00.

� NO RESP/NOT EQUIP for rear air suspension control module, go to Pinpoint Test A.

� SYSTEM PASSED, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and perform self-test diagnostics for the rear air suspension control module.

6. If the DTCs retrieved are related to the concern, go to Rear Air Suspension Control Module Diagnostic Trouble Code (DTC) Index to continue diagnostics.

7. If no DTCs related to the concern are retrieved, proceed to Symptom Chart to continue diagnostics.

Rear Air Suspension Control Module Diagnostic Trouble Code (DTC) Index

NOTE: If rear air suspension control module C251 is disconnected before rear air suspension control module C250, DTCs C1830, C1770, C1790 and C1795 will be retrieved and must be cleared before an accurate list of continuous DTCs can be retrieved. The DTCs C1441 and C1442 will only be retrieved when running the electronic variable orifice (EVO) functional test on the scan tool. The DTC C1897 will only be retrieved once per ignition switch cycle.

Rear Air Suspension Control Module Diagnostic Trouble Code (DTC) Index

Mechanical Electrical

� Restricted suspension movement � Excessive vehicle load � Cut, severed or crimped air line(s) � Incorrectly mounted, damaged or disconnected height sensor � Damaged air spring(s)

� Central junction box (CJB) Fuse: � 8 (10A) � 17 (10A)

� Battery junction box (BJB) Fuse 12 (30A) � Loose or corroded connectors � Air suspension switch � Damaged air spring solenoid(s)

DTC Description Source Action

B1317 Battery Voltage High Rear Air Suspension Control Module

GO to Pinpoint Test C.

B1318 Battery Voltage Low Rear Air Suspension Control Module

GO to Pinpoint Test C.

B1342 ECU Is Defective Rear Air Suspension Control Module

INSTALL a new rear air suspension control module. REFER to Module—Air Suspension Control. TEST the system for normal operation.

C1441 Steering Sensor Channel A Circuit Failure Rear Air Suspension Control Module

REFER to Section 211-00.

C1442 Steering Sensor Channel B Circuit Failure Rear Air Suspension Control Module


C1722 Air Suspension Height Sensor Power Circuit Short to Power


GO to Pinpoint Test D.

C1723 Air Suspension Height Sensor Power Circuit Short to Ground


GO to Pinpoint Test E.

C1760 Air Suspension Rear Height Sensor High Signal Circuit Failure


GO to Pinpoint Test F.

C1763 Air Suspension Rear Height Sensor High Signal Circuit Short to Ground


GO to Pinpoint Test G.

C1765 Air Suspension Rear Height Sensor Low Signal Circuit Failure


GO to Pinpoint Test F.

C1768 Air Suspension Rear Height Sensor Low Signal Circuit Short to Ground


GO to Pinpoint Test H.

C1770 Air Suspension Vent Solenoid Output Circuit Failure Rear Air Suspension Control Module

GO to Pinpoint Test I.



Rear Air Suspension Control Module Parameter Identification (PID) Index

Rear Air Suspension Control Module Parameter Identification (PID) Index

Rear Air Suspension Control Module Active Command Index

Rear Air Suspension Control Module Active Command Index

Symptom Chart

C1773 Air Suspension Vent Solenoid Output Circuit Short to Ground


GO to Pinpoint Test J.

C1790 Air Suspension LR Air Spring Solenoid Output Circuit Failure


GO to Pinpoint Test K.

C1793 Air Suspension LR Air Spring Solenoid Output Circuit Short to Ground


GO to Pinpoint Test L.

C1795 Air Suspension RR Air Spring Solenoid Output Circuit Failure


GO to Pinpoint Test M.

C1798 Air Suspension RR Air Spring Solenoid Output Circuit Short to Ground


GO to Pinpoint Test N.

C1813 Air Suspension Vent Request Exceeded Max Timing


GO to Pinpoint Test O.

C1818 Air Suspension Air Compressor Request Exceeded Max Timing


GO to Pinpoint Test P.

C1830 Air Compressor Relay Circuit Failure Rear Air Suspension Control Module

GO to Pinpoint Test Q.

C1832 Air Compressor Relay Circuit Short to Power Rear Air Suspension Control Module

GO to Pinpoint Test R.

C1840 Air Suspension Switch Circuit Failure Rear Air Suspension Control Module

GO to Pinpoint Test S.

C1842 Air Suspension Switch Circuit Short to Power Rear Air Suspension Control Module

GO to Pinpoint Test D.

C1897 Steering VAPS Circuit Loop Failure Rear Air Suspension Control Module


U1041 SPC Invalid or Missing Data for Vehicle Speed ABS CARRY OUT the ABS Self-Test.

PID Description Expected Values

AS_COMP Air Suspension Compressor Status OFF---, OFFO--, OFF-B-, OFF--G, OFFO-G, OFFOB-, OFF-BG, OFFOBG, ON---, ONO--, ON-B-, ON--G, ONO-G, ONOB-, ON-BG, ONOBG

AS_TRIM Air Suspension Accurate Trim TRIM, notTRIM

AS_VENT Air Suspension Vent Solenoid Status OFF---, OFFO--, OFF-B-, OFF--G, OFFO-G, OFFOB-, OFF-BG, OFFOBG, ON---, ONO--, ON-B-, ON--G, ONO-G, ONOB-, ON-BG, ONOBG

AS_WARN Air Suspension Warning Indicator ON, OFF

ASR_HGT Rear Digital Height Sensor TRIM, HIGH, LOW, HGND, LGND, H_LGND, L_HGND

CCNTRAS Number of Continuous DTCs in Rear Air Suspension Control Module

One count per bit

D_DRRAS Driver Door Input to Rear Air Suspension Control Module AJAR, CLOSED

FUEL_DR Fuel Door Ajar AJAR, CLOSED

IGN_RAS Ignition RUN/START Input to Rear Air Suspension Control Module

ACCY, RUN, START, OFF

LR_SOL Air Suspension LR Air Spring Solenoid Status OFF---, OFFO--, OFF-B-, OFF--G, OFFO-G, OFFOB-, OFF-BG, OFFOBG, ON---, ONO--, ON-B-, ON--G, ONO-G, ONOB-, ON-BG, ONOBG

P_DRRAS Passenger Door Ajar Input to Rear Air Suspension Control Module

AJAR, CLOSED

RR_SOL Air Suspension LR Air Spring Solenoid Status OFF---, OFFO--, OFF-B-, OFF--G, OFFO-G, OFFOB-, OFF-BG, OFFOBG, ON---, ONO--, ON-B-, ON--G, ONO-G, ONOB-, ON-BG, ONOBG

VAPS_IN VAPSII Input Current Loop 100/255

VAPSDRV VAPS Driver Output State OFF---, OFFO--, OFF-B-, OFF--G, OFFO-G, OFFOB-, OFF-BG, OFFOBG, ON---, ONO--, ON-B-, ON--G, ONO-G, ONOB-, ON-BG, ONOBG

VAPSOUT VAPSII Output Current Set Point 100/255

VBATRAS Battery Voltage Value to Rear Air Suspension Control Module

UDR 0V, OVR 5V, volts

VSS_RAS Vehicle Speed Input to Rear Air Suspension Control Module

MPH

Active Command Display Action

MODULE SLEEP — —

REAR AIR SUSPENSION CONTROL MODULE COMPRESSR ON, OFF

VENT ON, OFF

LR SOL ON, OFF

RR SOL ON, OFF

HGT POWER ON, OFF

VAPSII OUTPUT PULSE CONTROL VAPSIIOUT 0-100%



NOTE: Refer to the Wiring Diagrams for connector numbers stated in the Pinpoint Tests.

Pinpoint Tests

PINPOINT TEST A: NO COMMUNICATION WITH THE REAR AIR SUSPENSION CONTROL MODULE

Symptom Chart

Condition Possible Sources Action

� No communication with the module — rear air suspension control module

� CJB Fuse 8 (10A), 17 (10A).

� Circuitry. � Data link connector

(DLC). � Rear air suspension

control module.

� GO to Pinpoint Test A.

� Unable to enter self-test � Rear air suspension control module.

� GO to Pinpoint Test B.

� Did not detect open and close door signals � Circuitry. � Door ajar switch. � Lighting control module

(LCM). � Rear air suspension

control module.

� GO to Pinpoint Test T.

� The compressor is inoperative � Circuitry. � Air compressor relay. � Air compressor.

� GO to Pinpoint Test U.

� The air compressor continuously cycles with the ignition switch in the OFF position and no DTC is set

� Circuitry. � Air compressor relay. � Rear air suspension

control module.

� GO to Pinpoint Test V.

� Air suspension system works with air suspension switch in the OFF position

� Air suspension switch. � INSTALL a new air suspension switch. REFER to Switch—Air Suspension. TEST the system for normal operation.

� Uneven vehicle height � Pneumatic fault. � Air suspension height

sensor. � Air spring solenoid. � Air compressor. � Air spring. � Rear air suspension

control module.

� GO to Pinpoint Test P.

CONDITIONS DETAILS/RESULTS/ACTIONS

A1 CHECK CIRCUIT 296 (WH/VT) FOR AN OPEN

Rear Air Suspension Control Module C250

Measure the voltage between rear air suspension control module C250 Pin 16, Circuit 296 (WH/VT), harness side and ground.

� Is the voltage greater than 10 volts?

Yes GO to A2.

No REPAIR the circuit. REPEAT the Self-Test.

A2 CHECK CIRCUIT 418 (DG/YE) FOR AN OPEN

Measure the voltage between rear air suspension control module C250 Pin 1, Circuit 418 (DG/YE), harness side and ground.



PINPOINT TEST B: UNABLE TO ENTER SELF-TEST

PINPOINT TEST C: DTC B1317 — BATTERY VOLTAGE HIGH, DTC B1318 — BATTERY VOLTAGE LOW


Yes GO to A3.


A3 CHECK CIRCUIT 570 (BK/WH) FOR AN OPEN

Measure the resistance between rear air suspension control module C250 Pin 6, Circuit 570 (BK/WH), harness side and ground.

� Is the resistance less than 5 ohms?

Yes REFER to Section 418-00.



B1 CHECK THE COMMUNICATIONS TO THE REAR AIR SUSPENSION CONTROL MODULE

Check the communication to the rear air suspension control module.

� Does scan tool communicate to the rear air suspension control module?

Yes INSTALL a new rear air suspension control module. REFER to Module—Air Suspension Control. REPEAT the Self-Test.

No GO to Pinpoint Test A.


C1 CHECK BATTERY VOLTAGE

NOTE: A recent jump start may cause these DTCs to set.

Measure the battery voltage between the positive and negative battery posts with the key ON engine OFF (KOEO) and with the engine running.

� Is the battery voltage between 10 and 13 volts with KOEO, and between 11 and 17 volts with the engine



PINPOINT TEST D: DTC C1722 — AIR SUSPENSION HEIGHT SENSOR CIRCUIT SHORT TO POWER, DTC C1842 — AIR SUSPENSION SWITCH CIRCUIT SHORT TO POWER

running?

Yes GO to C2.

No REFER to Section 414-00.

C2 CHECK CIRCUIT 570 (BK/WH) FOR AN OPEN


Measure the resistance between rear air suspension control module C250 Pin 6, Circuit 570 (BK/WH), harness side and ground.



No REPAIR the circuit. CLEAR the DTCs. REPEAT the Self-Test.


D1 CHECK CIRCUIT 635 (YE) FOR SHORT TO POWER


Air Suspension Switch C458

Measure the voltage between rear air suspension control module C250 Pin 2, Circuit 635 (YE), harness side and ground.

� Is voltage present?

Yes REPAIR the circuit. CLEAR the DTCs. REPEAT the Self-Test.

No



PINPOINT TEST E: DTC C1723 — AIR SUSPENSION HEIGHT SENSOR POWER CIRCUIT SHORT TO GROUND

GO to D2.

D2 CHECK CIRCUIT 417 (VT/OG) FOR SHORT TO POWER

Air Suspension Height Sensor C468

Measure the voltage between rear air suspension control module C251 Pin 22, Circuit 417 (VT/OG), harness side and ground.



No INSTALL a new rear air suspension control module. REFER to Module—Air Suspension Control. REPEAT the Self-Test.


E1 CHECK CIRCUIT 635 (YE) FOR SHORT TO GROUND



Measure the resistance between rear air suspension control module C250 Pin 2, Circuit 635 (YE), harness side and ground.

� Is the resistance greater than 10,000 ohms?

Yes GO to E2.


E2 CHECK CIRCUIT 417 (VT/OG) FOR SHORT TO GROUND



PINPOINT TEST F: DTC C1760 — AIR SUSPENSION REAR HEIGHT SENSOR HIGH SIGNAL CIRCUIT FAILURE, DTC C1765 — AIR SUSPENSION REAR HEIGHT SENSOR LOW SIGNAL CIRCUIT FAILURE


Measure the resistance between rear air suspension control module C251 Pin 22, Circuit 417 (VT/OG), harness side and ground.


Yes RECONNECT air suspension switch C458. GO to E3 .


E3 CHECK AIR SUSPENSION SWITCH FOR SHORT TO GROUND

Measure the resistance between rear air suspension control module C250 Pin 2, Circuit 635 (YE), harness side and ground.


Yes RECONNECT air suspension height sensor C468. GO to E4 .

No INSTALL a new air suspension switch. REFER to Switch—Air Suspension. CLEAR the DTCs. REPEAT the Self-Test.

E4 CHECK THE AIR SUSPENSION HEIGHT SENSOR

Disconnect the lower end of the air suspension height sensor (5359).

Monitor the rear air suspension control module PID ASR_HGT.

While monitoring the rear air suspension control module PID ASR_HGT display, slowly extend and compress the air suspension height sensor through the full range of motion.

� Does the rear air suspension control module PID ASR_HGT indicate HIGH, TRIM and LOW?


No INSTALL a new air suspension height sensor. REFER to Height Sensor—Air Suspension. CLEAR the DTCs. REPEAT the Self-Test.




F1 CHECK CIRCUIT 428 (OG/BK) FOR SHORT TO POWER



Measure the voltage between rear air suspension control module C250 Pin 3, Circuit 428 (OG/BK), harness side and ground.



No GO to F2.

F2 CHECK CIRCUIT 427 (PK/BK) FOR SHORT TO POWER

Measure the voltage between rear air suspension control module C250 Pin 17, Circuit 427 (PK/BK), harness side and ground.



No GO to F3.

F3 CHECK THE HEIGHT SENSOR CIRCUITRY FOR AN OPEN

Measure the resistance between rear air suspension control module electrical connectors and height sensor electrical connectors; refer to the following table:

Rear Air Suspension Control Module Air Suspension Height Sensor Circuit No.

C250 Pin 3 C468 Pin 4 428 (OG/BK)

C250 Pin 17 C468 Pin 2 427 (PK/BK)

C251 Pin 8 C468 Pin 1 432 (BK/PK)

C251 Pin 22 C468 Pin 3 417 (VT/OG)



PINPOINT TEST G: DTC C1763 — AIR SUSPENSION HEIGHT REAR SENSOR HIGH SIGNAL CIRCUIT SHORT TO GROUND

� Are the resistances less than 5 ohms?

Yes RECONNECT the rear air suspension control module C250, C251 and air suspension height sensor C468. GO to F4 .

No REPAIR the circuit in question. CLEAR the DTCs. REPEAT the Self-Test.

F4 CHECK THE AIR SUSPENSION HEIGHT SENSOR

Disconnect the lower end of the air suspension height sensor.




Yes INSTALL a new rear air suspension control module. REFER to Module—Air Suspension Control . REPEAT the Self-Test.

No INSTALL a new air suspension height sensor. REFER to Height Sensor—Air Suspension. REPEAT the Self-Test.


G1 CHECK CIRCUIT 427 (PK/BK) FOR SHORT TO GROUND




PINPOINT TEST H: DTC C1768 — AIR SUSPENSION REAR HEIGHT SENSOR LOW SIGNAL CIRCUIT SHORT TO GROUND


Measure the resistance between rear air suspension control module C250 Pin 17, Circuit 427 (PK/BK), harness side and ground.


Yes RECONNECT the rear air suspension control module C250 and air suspension height sensor C468. GO to G2 .


G2 CHECK THE AIR SUSPENSION HEIGHT SENSOR








H1 CHECK CIRCUIT 428 (OG/BK) FOR SHORT TO GROUND



Measure the resistance between rear air suspension control module C250 Pin 3, Circuit 428 (OG/BK), harness side and ground.



PINPOINT TEST I: DTC C1770 — AIR SUSPENSION VENT SOLENOID OUTPUT CIRCUIT FAILURE


Yes RECONNECT the rear air suspension control module C250 and air suspension height sensor C468. GO to H2 .


H2 CHECK THE AIR SUSPENSION HEIGHT SENSOR








I1 CHECK CIRCUIT 421 (PK) FOR SHORT TO POWER


Air Compressor C158

Measure the voltage between rear air suspension control module C251 Pin 24, Circuit 421 (PK), harness side and ground.





No GO to I2.

I2 CHECK CIRCUIT 421 (PK) FOR AN OPEN

Measure the resistance between rear air suspension control module C251 Pin 24, Circuit 421 (PK), harness side and air compressor C158 Pin 2, Circuit 421 (PK), harness side.


Yes GO to I3.


I3 CHECK CIRCUIT 57 (BK) FOR AN OPEN

Measure the resistance between air compressor C158 Pin 4, Circuit 57 (BK), harness side and ground.


Yes RECONNECT air compressor C158. GO to I4 .


I4 CHECK THE AIR COMPRESSOR

Measure the resistance between rear air suspension control module C251 Pin 24, Circuit 421 (PK), harness side and ground.

� Is the resistance approximately 31 ohms?



PINPOINT TEST J: DTC C1773 — AIR SUSPENSION VENT SOLENOID OUTPUT CIRCUIT SHORT TO GROUND

PINPOINT TEST K: DTC C1790 — AIR SUSPENSION LR AIR SPRING SOLENOID OUTPUT CIRCUIT FAILURE


No INSTALL a new air compressor (5319). REFER to Air Compressor. CLEAR the DTCs. REPEAT the Self-Test.


J1 CHECK CIRCUIT 421 (PK) FOR SHORT TO GROUND


Air Compressor C158



Yes RECONNECT air compressor C158. GO to J2 .


J2 CHECK THE AIR COMPRESSOR




No INSTALL a new air compressor. REFER to Air Compressor. CLEAR the DTCs. REPEAT the Self-Test.


K1 CHECK CIRCUIT 1114 (BN/PK) FOR SHORT TO POWER




Measure the voltage between rear air suspension control module C251 Pin 13, Circuit 1114 (BN/PK), harness side and ground.



No GO to K2.

K2 CHECK THE REAR AIR SUSPENSION CONTROL MODULE

LR Air Spring Solenoid C492

Measure the resistance between rear air suspension control module C251 Pin 13, Circuit 1114 (BN/PK), harness side and ground.



No GO to K3.

K3 CHECK CIRCUIT 1114 (BN/PK) FOR AN OPEN

Measure the resistance between rear air suspension control module C251 Pin 13, Circuit 1114 (BN/PK), harness side and LR air spring solenoid C492, Circuit 1114 (BN/PK), harness side.


Yes



PINPOINT TEST L: DTC C1793 — AIR SUSPENSION LR AIR SPRING SOLENOID OUTPUT CIRCUIT SHORT TO GROUND

GO to K4.


K4 CHECK CIRCUIT 57 (BK) FOR AN OPEN

Measure the resistance between LR air spring solenoid C492, Circuit 57 (BK), harness side and ground.


Yes INSTALL a new LR air spring solenoid. REFER to Solenoid Valve—Functional.. CLEAR the DTCs. REPEAT the Self-Test.



L1 CHECK THE REAR AIR SUSPENSION CONTROL MODULE





No GO to L2.

L2 CHECK CIRCUIT 1114 (BN/PK) FOR SHORT TO GROUND

LR Air Spring Solenoid C492




PINPOINT TEST M: DTC C1795 — AIR SUSPENSION RR AIR SPRING SOLENOID OUTPUT CIRCUIT FAILURE





M1 CHECK CIRCUIT 1115 (TN/WH) FOR SHORT TO POWER


Measure the voltage between rear air suspension control module C251 Pin 25, Circuit 1115 (TN/WH), harness side and ground.



No GO to M2.

M2 CHECK THE REAR AIR SUSPENSION CONTROL MODULE

RR Air Spring Solenoid C467

Measure the resistance between rear air suspension control module C251 Pin 25, Circuit 1115 (TN/WH), harness side and ground.



No GO to M3.

M3 CHECK CIRCUIT 1115 (TN/WH) FOR AN OPEN



PINPOINT TEST N: DTC C1798 — AIR SUSPENSION RR AIR SPRING SOLENOID OUTPUT CIRCUIT SHORT TO GROUND

Measure the resistance between rear air suspension control module C251 Pin 25, Circuit 1115 (TN/WH), harness side and RR air spring solenoid C467, Circuit 1114 (BN/PK), harness side.


Yes GO to M4.


M4 CHECK CIRCUIT 57 (BK) FOR AN OPEN

Measure the resistance between RR air spring solenoid C467, Circuit 57 (BK), harness side and ground.


Yes INSTALL a new RR air spring solenoid. REFER to Solenoid Valve—Functional.. CLEAR the DTCs. REPEAT the Self-Test.



N1 CHECK THE REAR AIR SUSPENSION CONTROL MODULE





No GO to N2.

N2 CHECK CIRCUIT 1115 (TN/WH) FOR SHORT TO GROUND



PINPOINT TEST O: DTC C1813 — AIR SUSPENSION VENT REQUEST EXCEEDED MAXIMUM TIMING

NOTE: Repair all other DTCs before repairing DTC C1813.

NOTE: It may become necessary to partially vent air from the rear air springs during this Pinpoint Test.

RR Air Spring Solenoid C467






O1 CHECK THE AIR SUSPENSION HEIGHT SENSOR

Check the air suspension height sensor for correct installation at the upper and lower ball stud brackets.

Check the air suspension height sensor mounting brackets for damage.

� Are the air suspension height sensor and mounting brackets OK?

Yes GO to O2.

No REPAIR as necessary. CLEAR the DTCs. REPEAT the Self-Test.

O2 CHECK AIR SUSPENSION HEIGHT SENSOR OPERATION





Yes



GO to O3.


O3 CHECK PNEUMATIC SYSTEM — VENT LR AIR SPRING

NOTE: If fluid is present when disconnecting the air line, clear the air lines; refer to Air Line Fluid Purge. Check the air compressor drier for water or the air compressor for oil contamination.

NOTE: The rear springs must be partially inflated in order to perform this test. Add air as necessary.

Disconnect the air compressor drier air line.

Trigger the rear air suspension control module active command LR SOL ON.

� Does the air vent from the air compressor drier air line?

Yes Trigger the rear air suspension control module active command LR SOL OFF. GO to O4 .

No Trigger the rear air suspension control module active command LR SOL OFF. GO to O5 .

O4 CHECK PNEUMATIC SYSTEM — VENT RR AIR SPRING

NOTE: The rear springs must be partially inflated in order to perform this test. Add air as necessary.

Trigger the rear air suspension control module active command RR SOL ON.

� Does the air vent from the air compressor drier air line?

Yes Trigger the rear air suspension control module active command RR SOL OFF. GO to O6 .

No Trigger the rear air suspension control module active command RR SOL OFF. GO to O5 .

O5 CHECK PNEUMATIC SYSTEM — AIR LINE

NOTE: If fluid is present when disconnecting the air line, clear the air lines; refer to Air Line Fluid Purge. Check the air compressor drier for water or the air compressor for oil.

Disconnect the suspected rear air spring solenoid air line.

Connect Vacuum Tester to the air line and try to pull a vacuum.

� Can a vacuum be developed?

Yes REPAIR or INSTALL a new air line. CLEAR the DTCs. REPEAT the Self-Test.

No INSTALL a new air spring solenoid. REFER to Solenoid Valve—Functional.. CLEAR the DTCs. REPEAT the Self-Test.

O6 CHECK VENT SOLENOID OPERATION

Disconnect the air line at the snorkel.

Connect Vacuum Tester to the snorkel air line and try to pull a vacuum.

Trigger the rear air suspension control module active command VENT ON.

Try to pull a vacuum again.

� Can a vacuum be developed with the rear air suspension control module active command VENT OFF

and no vacuum developed with the rear air suspension control module active command VENT ON?

Yes INSTALL a new rear air suspension control module; REFER to Module—Air Suspension Control. REPEAT the Self-Test.

No If no vacuum can be developed with the rear air suspension control module active command VENT OFF, GO to O7 . If a vacuum can be developed with the rear air suspension control module active command VENT ON, GO to O8 .

O7 CHECK THE AIR LINE AND CONNECTIONS

Check the air line and connections between Vacuum Tester and the air compressor.

� Are the air line and connections OK?

Yes INSTALL a new air compressor. REFER to Air Compressor. CLEAR the DTCs. REPEAT the Self-Test.


O8 CHECK AIR COMPRESSOR DRIER

Disconnect the air compressor drier.

Try to pull a vacuum.





PINPOINT TEST P: DTC C1818 — AIR SUSPENSION AIR COMPRESSOR REQUEST EXCEEDED MAXIMUM TIMING

NOTE: Repair all other DTCs except DTC C1813 before repairing DTC C1818.

No INSTALL a new air compressor drier. CLEAR the DTCs. REPEAT the Self-Test.


P1 CHECK AIR SUSPENSION HEIGHT SENSOR

Check the air suspension height sensor for correct installation at the upper and lower ball stud brackets.

Check the air suspension height sensor mounting brackets for damage.

� Are the air suspension height sensor and mounting brackets OK?

Yes GO to P2.


P2 CHECK AIR SUSPENSION HEIGHT SENSOR OPERATION





Yes GO to P3.


P3 CHECK OPERATION OF AIR COMPRESSOR

CAUTION: If the air compressor runs in this test, do not allow the air compressor to run for more than three minutes. The air compressor could overheat and stop operation due to an internal temperature sensitive thermal breaker.

Trigger the rear air suspension control module active command COMPRESSR ON.

� Does the air compressor run?

Yes Trigger the rear air suspension control module active command COMPRESSR OFF. GO to P11 .

No Trigger the rear air suspension control module active command COMPRESSR OFF. GO to P4 .

P4 CHECK AIR COMPRESSOR AFTER COOL DOWN PERIOD


Allow the vehicle to sit for 60 minutes to give the air compressor time to cool off.

Trigger the rear air suspension control module active commands VENT ON and COMPRESSR ON.



� Does the air compressor run?

Yes Trigger the rear air suspension control module active commands OFF. GO to P5 .

No Trigger the rear air suspension control module active commands OFF. GO to P6 .

P5 CHECK AIR COMPRESSOR THERMAL BREAKER


Trigger the rear air suspension control module active commands VENT ON and COMPRESSR ON for 60 seconds.

� Did the air compressor run for 60 seconds?

Yes The thermal breaker was overheated. CLEAR the DTCs. REPEAT the Self-Test.


P6 CHECK AIR COMPRESSOR RELAY

Air Compressor Relay

Check the air compressor relay connector pins and terminals for corrosion, bent or broken pins, moisture or other damage.

� Is the air compressor relay OK?

Yes GO to P7.


P7 CHECK CIRCUIT 1053 (LB/PK) FOR VOLTAGE

Measure the voltage between air compressor relay Pin 30, Circuit 1053 (LB/PK), harness side and ground.


Yes GO to P8.


P8 CHECK CIRCUITRY FROM AIR COMPRESSOR RELAY

Measure the resistance between air compressor relay Pin 87, Circuit 538 (GY/RD), harness side and ground.


Yes INSTALL a new air compressor relay. CLEAR the DTCs. REPEAT the Self-Test.



No GO to P9.

P9 CHECK CIRCUIT 538 (GY/RD) FOR AN OPEN

Air Compressor C158

Measure the resistance between air compressor relay Pin 87, Circuit 538 (GY/RD), harness side and air compressor C158 Pin 1, Circuit 538 (GY/RD), harness side.


Yes GO to P10.


P10 CHECK CIRCUIT 57 (BK) FOR AN OPEN





P11 CHECK AIR COMPRESSOR PRESSURE OUTPUT



Disconnect the air compressor air line.

Connect an air gauge (1,723 kPa [250 psi] maximum reading) with common fittings to the air compressor drier.

Trigger the rear air suspension control module active command COMPRESSR ON.

Trigger the rear air suspension control module active command COMPRESSR OFF after 30 seconds.

Wait five minutes.

Trigger the rear air suspension control module active command VENT ON long enough to relieve all pressure from the air compressor.

� Does the air compressor produce 896 kPa (130 psi) within 30 seconds and hold the developed

pressure?

Yes GO to P13.

No CHECK the test fittings for a possible air leak. GO to P12 .

P12 CHECK AIR COMPRESSOR DRIER

Disconnect the air compressor drier.

Connect the shop air to the air compressor drier port (air compressor side).

� Does the air compressor drier leak air?

Yes INSTALL a new air compressor drier. REFER to Drier. CLEAR the DTCs. REPEAT the Self-Test.




P13 CHECK AIR LINES

Connect Vacuum Tester to the air compressor drier air line.



Yes GO to P16.

No GO to P14.

P14 CHECK THE LR AIR SPRING SOLENOID FOR LEAK


Disconnect the LR air spring solenoid air line.

Plug the air line at the LR air spring solenoid.




No GO to P15.

P15 CHECK RR AIR SPRING SOLENOID FOR LEAK


Disconnect the RR air spring solenoid air line.

Plug the RR air spring solenoid air line.




No REPAIR or INSTALL a new air line as necessary. CLEAR the DTCs. REPEAT the Self-Test.

P16 CHECK LR AIR SPRING SOLENOID FOR OPERATION

WARNING: Do not over pressurize the rear springs. Over pressurized rear springs may rupture causing personal injury and damage to the vehicle.

NOTE: If the rear air spring is fully inflated, partially vent the air before conducting this test. If air cannot be vented, install a new LR air spring solenoid and clear the DTCs. Repeat the Self-Test.

Connect shop air to the air compressor drier air line.

Trigger the rear air suspension control module active command LR SOL ON.

Trigger the rear air suspension control module active command LR SOL OFF after 30 seconds or after the left rear is noticeably higher.

� Does the left rear raise up?

Yes GO to P17.

No CHECK the LR air spring for air leaks. INSTALL a new LR air spring, if necessary. If no air leak is found, INSTALL a new LR air spring solenoid. REFER to Solenoid Valve—Functional.. CLEAR the DTCs. REPEAT the Self-Test.

P17 CHECK RR AIR SPRING SOLENOID FOR OPERATION

WARNING: Do not over pressurize the rear springs. Over pressurized rear springs may rupture causing personal injury and damage to the vehicle.

NOTE: If the rear air spring is fully inflated, partially vent the air before conducting this test. If air cannot be vented, install a new RR air spring solenoid. Refer to Solenoid Valve—Functional. and clear the DTCs. Repeat the Self-Test.

Connect the shop air to the air compressor drier air line.

Trigger the air suspension active command RR SOL ON.

Trigger the air suspension active command RR SOL OFF after 30 seconds or after the right rear is noticeably higher.

� Does the right rear raise up?


No CHECK the RR air spring for an air leak. INSTALL a new RR air spring, if necessary. If no leak is found, INSTALL



PINPOINT TEST Q: DTC C1830 — AIR COMPRESSOR RELAY CIRCUIT FAILURE

a new RR air spring solenoid. REFER to Solenoid Valve—Functional.. CLEAR the DTCs. REPEAT the Self-Test.


Q1 CHECK AIR COMPRESSOR RELAY CONNECTOR


Check the air compressor relay connector pins and terminals for corrosion, bent or broken pins, moisture or other damage.

� Is the air compressor relay connector OK?

Yes GO to Q2.


Q2 CHECK POWER TO AIR SUSPENSION RELAY



Yes GO to Q3.


Q3 CHECK CIRCUIT 420 (DB/YE) FOR AN OPEN/SHORT TO GROUND


Measure the resistance between rear air suspension control module C251 Pin 23, Circuit 420 (DB/YE), harness side and air compressor relay Pin 85, Circuit 420 (DB/YE) harness side; and between rear air suspension control module C251 Pin 23, Circuit 420 (DB/YE), harness side and ground.

� Is the resistance less than 5 ohms between the rear air suspension control module and air compressor

relay, and greater than 10,000 ohms between the rear air suspension control module and ground?

Yes GO to Q4.


Q4 CHECK AIR COMPRESSOR RELAY COIL FOR AN OPEN

Measure the resistance between air compressor relay Pin 86 and Pin 85 (component side).



PINPOINT TEST R: DTC C1832 — AIR COMPRESSOR RELAY CIRCUIT SHORT TO POWER





R1 CHECK AIR COMPRESSOR RELAY COIL FOR SHORT


Measure the resistance between air compressor relay Pin 86 and Pin 85 (component side).



No GO to R2.

R2 CHECK CIRCUIT 420 (DB/YE) FOR SHORT TO POWER


Measure the voltage between rear air suspension control module C251 Pin 23, Circuit 420 (DB/YE), harness side and ground.




PINPOINT TEST S: DTC C1840 — AIR SUSPENSION SWITCH CIRCUIT FAILURE




S1 CHECK CIRCUIT 635 (YE) FOR AN OPEN



Measure the resistance between rear air suspension control module C250 Pin 2, Circuit 635 (YE), harness side and air suspension switch C458, Circuit 635 (YE), harness side.


Yes GO to S2.


S2 CHECK CIRCUIT 417 (VT/OG) FOR AN OPEN

Measure the resistance between rear air suspension control module C251 Pin 22, Circuit 417 (VT/OG), harness side and air suspension switch C458, Circuit 417 (VT/OG), harness side.


Yes GO to S3.


S3 CHECK AIR SUSPENSION SWITCH FOR AN OPEN

Place the air suspension switch in the ON position.

Measure the resistance between air suspension switch pins (component side).



PINPOINT TEST T: DID NOT DETECT OPEN AND CLOSE DOOR SIGNALS

PINPOINT TEST U: THE COMPRESSOR IS INOPERATIVE



No INSTALL a new air suspension switch. REFER to Switch—Air Suspension. CLEAR the DTCs. REPEAT the Self-Test.


T1 CHECK THE COURTESY LIGHTS

Open a door.

� Did the courtesy lights illuminate?

Yes GO to T2.

No REFER to Section 417-02.

T2 CHECK REAR AIR SUSPENSION CONTROL MODULE

Monitor the rear air suspension control module PID D_DRRAS.

Open and close a door.

� Does the rear air suspension control module PID D_DRRAS indicate AJAR when open and CLOSED when closed?

Yes The system is OK.



U1 CHECK CIRCUIT 1053 (LB/PK) FOR AN OPEN






Yes GO to U2.


U2 CHECK CIRCUITRY FROM AIR COMPRESSOR RELAY

Measure the resistance between air compressor relay Pin 87, Circuit 538 (GY/RD) and ground.


Yes INSTALL a new air compressor relay. REPEAT the Self-Test.

No GO to U3.

U3 CHECK CIRCUIT 538 (GY/RD) FOR AN OPEN

Air Compressor C158

Measure the resistance between air compressor relay Pin 87, Circuit 538 (GY/RD), harness side and air compressor C158 Pin 1, Circuit 538 (GY/RD), harness side.


Yes GO to U4.


U4 CHECK CIRCUIT 57 (BK) FOR AN OPEN





PINPOINT TEST V: THE AIR COMPRESSOR CONTINUOUSLY CYCLES WITH THE IGNITION SWITCH IN THE OFF POSITION AND NO DTC IS SET

Yes INSTALL a new air compressor. REFER to Air Compressor. REPEAT the Self-Test.



V1 CHECK FOR MODULE ACTIVITY

NOTE: The rear air suspension control module is powered for approximately 60 minutes after the ignition switch is placed in the OFF position. During this time, the air suspension will correct for vehicle weight by raising the vehicle.

Verify the air compressor still cycles 70 minutes after the ignition switch is placed in the OFF position.

� Does the air compressor still cycle after the air suspension module powers down?

Yes GO to V2.

No The system is OK.

V2 CHECK THE REAR AIR SUSPENSION CONTROL MODULE


� Does the air compressor still cycle?

Yes GO to V3.


V3 CHECK THE AIR COMPRESSOR RELAY


� Does the air compressor still cycle?

Yes REPAIR Circuit 538 (GY/RD). REPEAT the Self-Test.

No INSTALL a new air compressor relay. REPEAT the Self-Test.



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