Service Bulletin Bulletin No.: 02-08-49-007 Date: September 2002

Chevrolet / GMC

Technical

Subject: Center Console Lid Hard To Open Or Close (Lubricate Center Console Lid Latch)

Models: 1999-2003 Chevrolet Silverado, Suburban, Tahoe 1999-20003 GMC Sierra, Yukon, Yukon XL with Split Front Seats (RPO AE7) Condition: Some customers may comment on a center console lid that is hard

to open or close. Cause: Lack of lubrication on the center console lid latch may cause this

condition. Correction: Apply GM Dri Slide® Lubricant, P/N 1052948 to the center console

lid latch using the following procedure:

1. Open the center console lid. If the lid will not open, press in the center console latch handle button and give the top of the center console lid a sharp rap with your hand in order to open the lid.

2. Working through the opening in the latch trim plate, apply a small amount of lubricant to the center console latch, while operating the center console latch. Operating the center console latch while spraying the lubricant will help work the lubricant into the latch mechanism. It is not necessary to remove the center console latch trim plate.

3. Open and close the center console lid several times in order to verify the proper operation of the lid latch.

Service Bulletin

Bulletin No.: 02-06-01-022A Date: November 2002

Chevrolet/GMC

Information

Subject: Information on Engine Ticking Models: 2001-2003 Chevrolet Silverado 2003 Chevrolet Kodiak C4500/C5500 Series 2001-2003 GMC Sierra 2003 GMC Topkick C4500/C5500 Series with 6.6L Duramax™ Diesel Engine (VIN 1 – RPO LB7)

Some of the above vehicles may exhibit a random ticking noise that is most audible on an engine with a coolant temperature of 70°C (158°F) or higher and from idle to approximately 1500 RPM. The noise usually is most noticeable at the rear of the drivers’ side front wheel well. Customers may also comment about hearing a tick noise inside the vehicle at idle such as when sitting at a drive through window. All 6600 Duramax™ diesel engines have this condition; however, some are more audible than others. Engine build variation from engine to engine contributes to differences in perceived volume. All Duramax™ engines are manufactured to very close tolerances to meet the durability and reliability standards. This noise is caused by the relationship of the engine cylinder block, crankshaft journals, bearing inserts and the oil film. This relationship may allow a vibration that resonates through the cylinder block and is heard as a metallic ticking noise. The noise could be described as an irregular ticking or clacking sound, like random typing on a mechanical typewriter. This condition has been present in diesel engines produced for the last 20 or more years. The overall noise reduction in engines produced today makes this noise seem new when, in fact, it was masked by other noises in the past. Many manufacturers such as Isuzu, Hino, Mitsubishi, and Nissan report a similar condition in their diesel engines. Testing and engine teardowns with this condition reveal no condition that would affect reliability or durability of this engine.

Dealers should not attempt to compare any customer vehicles exhibiting this noise with other similar vehicle as the noise is different from vehicle to vehicle and this may lead to the incorrect conclusion that the vehicle has a condition. This noise is a normal operating characteristic of the engine. This noise has no short or long term effects on the engine. Do not attempt repairs for this noise.

Important: Replacing the engine or internal components for this noise will not reduce or eliminate the noise.

Please share the information found in this bulletin with customers who inquire about this condition. In they event they have additional questions or concerns, please contact Customer Assistance at the numbers listed below for further information. Division Number Deaf, Hearing

Impaired or Speech Impaired*

Chevrolet 1-800-222-1020 8:00 AM – 11:00 PM (EST)

1-800-833-2438 8 :00 AM – 11 :00 PM (EST)

GMC 1-800-462-8782 8:00 AM – 11:00 PM (EST)

1-800-462-8583 8:00 AM – 11:00 PM (EST)

Canada 1-800-263-3777 (English) 1-800-263-7854 (French) 7:30 AM – 11:30 PM (EST) (Mon-Fri) 7:30 AM – 6:00 PM (EST) (Sat)

1-800-263-3830 7:30 AM – 11:30 PM (EST) (Mon-Fri) 7:30 AM – 6:00 PM (EST) (Sat)

*Utilizes Telecommunication Devices for the Deaf/Text Telephones (TDD/TTY)

Service Bulletin

Bulletin No.: 02-07-30-011A Date: May 2002

Chevrolet/GMC

Information

Subject: Diagnostics for Possible Gear Indicator (PRNDL) Concerns (Blank PRNDL Display, Flashing PRNDL, Slow or No Engagement of Automatic Transmission, DTC U1000 or U1024 Set)

Models: 2001-2002 Chevrolet and GMC C/K Pickup Models (Silverado

or Sierra) with Allison® LCT1000 Automatic Transmission (RPO M74)

Blank PRNDL Display A blank PRNDL display may indicate a condition with the Park

Neutral Position (PNP) switch and/or one or more of the four signal circuits from the PNP to the Transmission Control Module (TCM).

1. Pin A, Circuit 771 (BLK/WHT) 2. Pin B, Circuit 773 (GRA) 3. Pin C, Circuit 776 (WHT) 4. Pin D, Circuit 772 (YEL)

Or, a blank PRNDL display may also occur if an out of line condition exists with the Serial Data Circuit (CKT 2470, yellow wire) from the TCM to Splice Pack 205.

Diagnostic Tip for Blank PRNDL Display

1. Connect the Tech 2® to the vehicle. 2. Power up the Tech 2®. 3. Does the Tech 2® communicate with the TCM? If no, inspect

the serial data circuit, CKT 2470 (yellow wire), between the TCM and Splice Pack 205. Specifically inspect connector C106, a five terminal connecter located below the left side underhood bused electrical center, directly beneath the red battery cable

terminal connection. Perform a mating terminal pull test on all of the terminals in this connector. Repair as required.

4. Observe the Gear Selected screen on the scan tool. The following values should be shown on the screen.

• “8” (shifter should be in the Park position) • “7” (shifter should be in the Reverse position) • “5” (shifter should be in the Drive position) • “3” (shifter should be in the Third gear position) • “2” (shifter should be in the Second gear position) • “1” (shifter should be in the First gear position) • “0” (shifter should be in the Neutral position) If the Gear Selected display does not match the shifter position in the vehicle, diagnose using the DTC P0706 or P0708 diagnosis chart in Service Information (SI) under Transmission/Transaxle/Automatic Transmission – Allison. Reference SI Document ID #769549 for the wiring schematic for this symptom. The PNP switch, as referenced in the Service Information, is known as the Neutral Start Back Up (NSBU) switch in the Parts Information.

Flashing PRNDL Display A flashing PRNDL display may be the result of incorrect sensor inputs or transmission abuse protection modes being received by the TCM. The following are some of these conditions. • The transfer case is/was in Neutral. • The transfer case is/was shifted into Neutral when the vehicle is moving. • A decrease of the input turbine speed was not detected when the gear selector was moved into any gear. • A low transmission fluid Level. • A misadjusted PNP/NSBU switch. • Turbine input speed or output speed sensor failure. • Failures of the shift solenoids to route the transmission oil to the proper clutch assemblies within the transmission. • Failures of the transmission clutch packs (C1 or C5 for first gear, C3 or C5 for Reverse). • Failure to detect proper line pressures when a gear range is selected, which may be the result of normal maintenance such as a transmission fluid change having been completed, or the transmission pan was removed for a filter replacement or other type service.

Transmission abuse protection modes are encountered when a customer performs one of the following types of maneuvers.

• Shifting from Neutral to Drive/Reverse when the engine RPM is greater than 1400 RPM. • Shifting from Drive to Reverse when the throttle position (TPS) is greater than 25%, such as rocking the vehicle when stuck in an attempt to free the vehicle. • When the transmission output speed is greater than 300 RPM from attempted changes in direction, such as Reverse to Drive, Drive to reverse or Neutral to Reverse shifts.

When the TCM encounters any one of the above conditions, the TCM will Flash the PRNDL and default the transmission to Neutral. A flashing PRNDL indicates something is/was incorrect. The transmission may need the attention of a qualified service technician.

Service Bulletin

Bulletin No.: 02-07-30-024 Date: May 2002

Buick/Cadillac/Chevrolet/GMC/Oldsmobile/Pontiac

Information

Subject: Diagnosis of Cracked or Broken Transmission Case. Models: 1990-1993 Buick Roadmaster, Estate Wagon 1990-1996 Cadillac Fleetwood 1990-1996 Chevrolet Caprice 1990-2002 Chevrolet Camaro 1990-2003 Chevrolet Corvette 1995-1996 Chevrolet Impala 2000-2003 Chevrolet Impala 1990-1992 Oldsmobile Custom Cruiser Wagon 1990-2002 Pontiac Firebird 1990-2003 Chevrolet & GMC C/K Models

(Silverado, Sierra, Avalanche, Suburban, Tahoe, Yukon, Yukon XL) 1990-2003 Chevrolet & GMC G-Van Models (Express, Savana) 1990-2003 Chevrolet & GMC M/L-Van Models (Astro, Safari) 1990-2003 Chevrolet & GMC S/T Models (S-10, Sonoma, Jimmy, Blazer, Trailblazer) 2000-2003 Cadillac Escalade 1991-1994 Oldsmobile Bravada 1996-2002 Oldsmobile Bravada with 4L60/4L60E/4L65E or 4L80ZE/4L85E or Allison® Series 1000 Automatic Transmission Diagnosing the cause of a cracked or broken transmission case requires additional diagnosis and repair or a repeat failure will occur. A cracked or broken transmission case is most often the result of abnormal external torsional forces acting on the transmission case. If none of the conditions listed below are apparent, an internal transmission component inspection may be required. Repairs of

this type may be the result of external damage or abuse for which General Motors id not responsible. They are not the result of defects in materials or workmanship. If in doubt, contact your General Motors Service Representative. The following items should be considered:

• It is important to inspect the vehicle for signs of an out of line condition, impact damage of foreign material to the following components:

• The transmission • The engine mounts • The transmission rear mount and crossmember

• Vehicle frame damage that alters the front to rear alignment of the driveshaft • The drive shafts (both front and rear) • The wheels (caked with mud, concrete, etc.) • The tires (roundness, lack of cupping, excessive balance weights) • The transfer case (if the vehicle is 4WD)

• A worn or damaged driveshaft U-Joint has shown to be a frequent cause of transmission case cracking, especially on vehicles that see extended periods of highway driving. Always inspect the U-Joint condition when diagnosing this condition. • For driveshaft damage or imbalance, Inspect the drive shafts (both front and rear) for dents, straightness/runout or signs of missing balance weights. Also, inspect for foreign material such as undercoat sprayed on the driveshaft. • The driveshaft working angles may be excessive or non-canceling, especially if the vehicle carrying height has been altered (lifted or lowered) or if the frame has been extended or modified. • Damaged or worn, upper or lower rear control arms or bushings. • A rear axle that is not seated in the rear spring properly (leaf spring vehicles). • Broken rear springs and or worn leaf spring bushings.

In some cases, the customer may not comment about a vibration but it is important to test-drive the vehicle while using the electronic vibration analysis tool in an attempt to locate the cause of the etorsional vibration. Refer to the Vibration Diagnosis and Correction sub-section of the appropriate Service Manual for more details on diagnosing and correcting vibrations.

Service Bulletin

Bulletin No.: 02-07-30-020 Date: May 2002

Chevrolet/GMC

Technical

Subject: Harsh or Delayed 2-1 Downshift, Neutral Feel at a Stop, Shift Busyness, DTCs P0708, P0847, P0872, P0875, P1711, P1713 (Reprogram TCM and, if necessary, Reprogram, PCM)

Models: 2001-2002 Chevrolet and GMC C/K 2500/3500 (3/4 and 1 ton)

Series Pickup Models (Silverado and Sierra) With Allison® Series 1000 Automatic Transmission (RPO M74) Condition: Some customers may comment on a harsh or delayed 2-1

downshift, a neutral feel at a stop or shift busyness (excessive shifting). Upon investigation, the technician may also find one or more of the following DTCs set:

• P0708 • P0847 • P0872 • P0875 • P1711 • P1713 These new calibrations will address the following conditions:

2001 2002 Delayed 2-1 downshift at a stop 2-1 downshift quality concerns Flare and bump on low speed

coast-down and throttle reapply Cold shift quality concerns

2-1 closed throttle neutral feel *Shift busyness Harsh 2-1 downshift DTC P0708, P0847, P0872, P0875,

P1711, P1713 Shift busyness 2-1 closed throttle neutral feel

Correction: Reprogram the Transmission Control Module (TCM) with the new

service calibrations, which were available from the Techline starting March 24, 2002 on the TIS2000 version 3.5 or later. These

calibrations are electronic calibrations and are NOT available from GMSPO.

Important: 2002 Vehicles with 8.1L Engine--- If the concern is shift busyness, the PCM must also be reflashed to

gain maximum benefit from the new TCM service calibration. This calibration was available from Techline starting March 10, 2002 on the TIS2000 version 3.0 or later. If the concern is not shift busyness, this step is not required.

This additional step is not required on vehicles with a 6.6L engine

(RPO LB7) or 2001 vehicles with an 8.1L engine (RPO L18).

Service Bulletin

Bulletin No.: 02-04-21-004 Date: April 2002

Chevrolet/GMC

Technical

Subject: “Service 4WD” Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch)

Models: 1999-2002 Chevrolet and GMC C/K Pickup and Utility Models (Silverado, Sierra, Avalanche, Suburban, Tahoe, Yukon, Yukon XL) with Four Wheel Drive and NVG 236/246 Transfer Case (RPO NP8)

Condition: Some customers may comment on the Service 4WD indicator illuminating. Upon investigation, the technician may find DTC B2725 set.

Cause: The condition may be due to an intermittent fault in the transfer

case shift control switch. Correction: Important: The transfer case shift control module should not need

replacement. DO NOT replace P/N 15749703 unless diagnosis points to the module as the malfunction.

Replace the transfer case shift control switch using published Service Information procedures.

Service Bulletin

Bulletin No.: 02-06-01-027 Date: August 2002

Chevrolet/GMC

Information

Subject: Higher Than Expected Oil Consumption Models: 2001-2003 Chevrolet Silverado 2500-3500 Series Models 2001-2003 GMC Sierra 2500-3500 Series Models 2003 Chevrolet Kodiak C4500-C5500 Series Models 2003 GMC Topkick C4500-C5500 Series Models with 6.6L Duramax™ Diesel Engine (VIN 1 – RPO LB7) Information on Engine Oil Consumption Guidelines for the 6.6L

Duramax Diesel Engine All engines require oil to lubricate and protect the load bearing

and internal moving parts from wear including cylinder walls, pistons and piston rings. When a piston moves down its cylinder, a thin film of oil is left on the cylinder wall. During the combustion process, part of this oil layer is consumed. As a result, varying rates of oil consumption are accepted as normal in all engines.

Oil Consumption Oil usage has a direct relationship with the amount of fuel used.

The harder an engine works, the more fuel and oil it will use. Therefore, oil usage as a factor of fuel usage is a more accurate indicator of acceptable oil consumption levels than vehicle mileage.

The accepted rate of oil consumption for the 6.6L Duramax™ Diesel engine is 0.946 liter (1 qt) within 379 liters (100 gallons) of fuel used. This rate only applies to vehicle sunder warranty, maintained in accordance with the appropriate maintenance schedule, driven at legal speeds and within design intent of the vehicle.

Many factors can affect an owner’s concern with oil consumption. Driving habits and vehicle maintenance vary from owner to owner. Thoroughly evaluate each case before deciding whether the vehicle in question has abnormal engine oil consumption.

Gasket and External Leaks Inspect the oil pans, engine covers, and the engine oil cooler for leakage. Inspect the turbocharger oil lines and fittings for signs of leakage. Inspect the turbocharger outlet pipe for signs of oil, indicating worn turbocharger shaft bushings or seals. Inspect for oil leakage into the engine coolant. Improper reading of the Oil Level Indicator (Dipstick) The vehicle must be parked on a level surface to obtain accurate oil level readings. Verify that the dipstick tube is fully seated in the block. When checking the oil level, make sure the dipstick is wiped clean before taking an oil level reading and fully depress the dipstick until the shoulder bottoms out on the dipstick tube. The dipstick should be the proper part number for the engine/vehicle that is being checked. Not Waiting Long Enough After Running Engine to Check Oil Level The vehicles should be allowed to sit for at least 15 minutes, after the engine has been shut off, before taking an oil level reading to assure the oil has had enough time to drain back into the crankcase. In order to ensure accurate results, the temperature of the oil should be close to the same temperature as the last time the oil level was checked. Improper Oil Fill After an Oil Change Following an oil change, verify that the proper amount and type of oil was put in the engine and that the oil level on the dipstick is not above the full mark or below the add marks. Refer to the Owners Manual or Service Manual for information on recommended oil quantity, viscosity, and quality. Diesel engines require a CH-4 or CG-4 oil rating. High Speed or High RPM Driving Continuous driving at high speeds/high RPMs may increase oil consumption. Because this may not always be an everyday occurrence, it is hard to determine exactly how much the oil economy will be affected. Towing or Heavy Usage Towing a trailer or hauling additional weight will increase oil consumption. Large frontal area trailers will further increase the work required from the engine, especially at highway speeds, and thus increases the rate of oil consumption.

PTO Operation Operation of a PTO will increase fuel and oil usage, as the PTO driven accessory uses engine power to operate. Crankcase Ventilation System Verify that the positive crankcase ventilation (PCV) system is operating properly. Blockages, restrictions or damage to the PCV system can result in increased oil use. Oil Dilution from Condensation On vehicles that are usually driven short distances, less than 8 km (5 mi), especially in colder weather, condensation generated from cold engine operation may not get hot enough to evaporate out of the oil. When this occurs, the dipstick may indicate that the oil level is over-full. Subsequent driving on a trip of sufficient length to enable normal engine operating temperature for 30 minutes or more, in order to vaporize excess moisture, may give the customer the impression of excessive oil consumption. Engine Temperature If an engine is run at overheated temperatures (see Owners Manual or Service Manual) for more than brief periods, oil will oxidize at a faster than normal rate. In addition, gaskets may distort, piston rings may stick, and excessive wear may result. Verify that all cooling system components are in proper working order. Engine Wear Piston scuffing, excessive piston-to-wall clearance, tapered or out of round cylinders, worn, damaged or improperly installed valve guides, seals and piston rings will all cause an increase in oil consumption. Measurement of Oil Consumption Engines require a period of time to BREAK IN so that moving parts are properly seated. Therefore, oil economy should not be tested until the vehicle has accumulated at least 8000 km (5000 mi) and the oil has been changed for the first time. During initial engine break-in periods before the first oil change, oil consumption may exceed 1.9 liters (2 quarts) or more per 379 liters (100 gallons) of fuel used. 1. Verify that the engine has no external leaks. Repair as

necessary. 2. Begin oil consumption test after next regularly scheduled oil and

filter change. Oil changes should not be performed during the test.

3. Verify that the engine is at normal operating temperature (see Owner’s Manual or Service Manual).

4. Park the vehicle on a level surface. 5. Wait at least 15 minutes, after the engine is shut off, before

checking the oil level to make sure that most of the oil has had time to drain back into the crankcase.

6. Verify that the oil level is at, but not above, the full mark on the dipstick and that the proper viscosity and quality oil are being used as recommended in the Owner’s Manual.

7. Dealer should record the vehicle mileage, date and engine hours at the start of the test.

8. Ask the customer to verify and record the date, odometer, oil level, fuel added, and engine hours, each time the vehicle is fueled, following steps 3-5 and return the vehicle to the dealership if the oil level is found at or below the add mark, 0.946 liter (1 qt) low, if possible. The dealer will add oil to return the oil level to full. If the oil level remains above the add mark, the customer should continue to operate the vehicle and verify the engine oil level until either the oil level drops to or below the add mark or at least 4800 KM (3000 mi) has accumulated since the test began before returning to the dealership for a final evaluation.

9. If the final evaluation shows that the engine uses more than 0.946 liter (1 qt) in 379 liters (100 gallons) of fuel used, follow the published symptom diagnostics as described in the appropriate Service Manual. If the oil consumption test shows that the engine uses less than 0.946 liter (1 qt) in 379 liters (100 gallons) of fuel used, explain to the customer that their engine meets the guidelines for oil consumption.

Service Bulletin

Bulletin No.: 02-07-30-004A Date: September 2002

Chevrolet/GMC

Information Subject: New Product Information – Grade Brake Features of Allison®

1000 Series Transmission Models: 2001-2003 Chevrolet Silverado Pickup Models 2001-2003 GMC Sierra Pickup Models with Allison® LCT1000 Series Automatic Transmission (RPO-

M74) The grade-braking algorithm’s primary purpose is to utilize engine

braking to slow a heavy vehicle on steep grades in order to reduce wear on the traditional braking system. The method used to slow the vehicle is by overriding the PRNDL position, effectively pre-selecting the next lower gear range automatically. Because the transmission is electronically controlled and there is no mechanical linkage that needs to be moved for a pre-select downshift, implementation of this algorithm can be done completely in software with no hardware modifications.

This algorithm takes into consideration several factors before commanding a pre-select downshift. These are the primary inputs:

• Throttle position • Brake state (The brake must be applied to activate grade

braking) • Vehicle acceleration/deceleration • Grade/Load • Vehicle speed The determination of the PRNDL position is made by a logic

subsystem. Several factors are calculated and weighted and then a sum is calculated. When this calculated sum surpasses a threshold, a PRNDL override is commanded.

Important: The shift speeds for grade-braking are controlled/determined as a

result of “Calculated Sum” logic. However, the grade-braking shift point will never be greater than the Pre-Select Shift Point.

The following charts provide the maximum Pre-Select (manual) shift points:

8.1L Gas Engine (RPO L18) with both 4.10 and 3.73 axle ratio Shift Transmission OSS RPM 5-4 4624 4-3 3266 3-2 2543 2-1 1474

For the L18 gas engine, maximum engine speed immediately

following a preselect or grade braking downshift can be as high as 4,650 RPM. After a grade braking downshift, if vehicle speed continues to increase, an upshift will occur at 5,000-RPM engine speed.

6.6L Diesel Engine (RPO LB7) with 3.73 axle ratio Shift Transmission OSS RPM 5-4 4017 4-3 2832 3-2 2196 2-1 1214

For the LB7 diesel engine, maximum speed immediately following a

preselect or grade braking downshift can be as high as 4,000 RPM. After a grade braking downshift, if vehicle speed continues to increase, an up shift will occur at 4,8000 RPM engine speed.

Some commonly asked questions on Grade-Braking. Important: Grade Braking is not intended to reduce the need for great care

by the driver when driving a heavy loaded vehicle down a grade. Drivers should continue to take all normal and appropriate actions to keel the vehicle under control at all times.

1. Does grade-braking feature work on level roadways while

trailing or hauling heavy loads and applying brakes?

The feature is actively calculating whether or not to command a downshift while on level roadways, but it is much less likely that it will

command a downshift under these conditions. The reason is that the Transmission Control Module (TCM) is using vehicle acceleration/deceleration as a determining factor. Since the vehicle is more likely to respond to vehicle brakes on level surfaces vs. on a grade, grade braking is less likely to command a downshift.

2. Does grade-braking work in Tow/Haul and normal mode? Yes, grade-braking is active in either mode.

3. Can I turn grade-braking off? No, automatic grade-braking is always an active part of the transmission control system.

4. Does Tow/Haul have to be selected?

No. In normal mode, the grade-braking feature will pre-select only the 5-4 downshift, whereas in Tow/Haul mode, grade-braking has ability to select the 5-4, 4-3, 3-2 downshifts. 5. When will I get a grade-breaking downshift? There is no “fixed”

shift point for a grade-braking downshift, however, the grade-braking downshift will never occur such that the engine speed following the shift exceeds GM Truck guidelines. Also, the grade-braking downshift will never occur without depressing the brake pedal.

6. To which gear will grade-braking downshift in each mode? The downshift will always be to the next lower range, ie.; it will not “skip” ranges. In the Tow/Haul mode, the grade-braking feature has ability to select the 5-4, 4-3, 3-2 downshifts. Normal mode grade-braking will not command downshifts below 4th range.

7. Does towing a trailer have any affect? Yes, the TCM calculates the affect of the added mass of the trailer/load.

8. How do I get out of a grade-braking shift? Grade-braking can be exited by depressing the throttle.

9. What happens if the vehicle is on ice and a grade-braking event occurs, and the vehicle begins to slip? Grade-braking monitors the front and rear wheel speeds and can determine if the vehicle is slipping. If a slip occurs, grade-braking will be exited and the transmission will up shift to the normal gear range depending on throttle position and transmission output shaft speed.

Service Bulletin Bulletin No.: 01-03-10-010A Date: September 2002

Chevrolet/GMC

Information

Subject: Inspection of Tire and Wheel Size Prior to Diagnosis of Transmission Shifts, Poor Performance, Speedometer, Cruise Control Concerns

Models: 2001-2002 Chevrolet Silverado Pickup Models 2001-2002 GMC Sierra Pickup Models

with Duramax™ Diesel Engine and Allison® Transmission Proper Diagnosis of engine, transmission, speedometer, and cruise control concerns must begin with an inspection of tire/wheel size.

• The 2500 series trucks have LT245/75R16E tires as standard equipment. • The 3500 series trucks have LT215/85R16D tires as standard equipment. A truck that has different tires and wheels will have Engine power/performance concerns, Transmission shift concerns, Speedometer registered speed concerns, and Cruise Control concerns. If a truck is found to have other than the above listed tire sizes, no further diagnosis should be undertaken until the original size tires and wheels have been reinstalled on the truck. The Engine Control Unit (ECM) and Transmission Control Module (TCM) use (RPM) and (VSS) inputs as operational parameters for engine torque, transmission shifting, cruise control operation and speedometer indicated vehicle speed. Calibrations for different tire/wheel combination are not available. Therefore changing of tire and/or wheel size should not be undertaken by dealerships or truck owners. Warranty Information Reinstalling the proper wheels and tires on the vehicle, prior to performing any diagnosis of the truck, would be truck owner responsibility and not a warranty repair.

Service Bulletin

Bulletin No.: 02-07-30-034 Date: September 2002

Chevrolet/GMC

Technical

Subject: Loss of Cruise Control, Decreased Pedal Dampening or Tip In Driveline Clunk (Inspect Wiring and NSBU Switch)

Models: 2001 Chevrolet Silverado Pickup Models 2001 GMC Sierra Pickup Models with 6.6L Duramax™ Diesel Engine (VIN 1 –RPO LB7) and Allison® Automatic Transmission (RPO M74) Condition: Some customers may comment on a loss of cruise control function,

decreased accelerator pedal dampening or a tip in driveline clunk noise. Additionally, the customer may perceive a change in the sound of the running engine.

Cause: Circuit 1786 ORN/BLK from the Park/Neutral Start Back-Up (NSBU)

switch may be shorted to ground, or the NSBU may not be switching correctly and grounding the circuit internally.

Correction: Using Service Manual procedures, repair any short to ground on the

1786 circuit or replace the Park/Neutral Start Back-Up Switch if internally shorted to ground. Also, be sure that the vehicle contains the latest PCM Calibration.

Service Bulletin

Bulletin No.: 02-06-04-048 Date: September 2002

Chevrolet/GMC

Service Manual Update

Subject: Revised DTC P0540 Models: 2001-2002 Chevrolet Silverado Pickup Models 2001-2002 GMC Sierra Pickup Models with 6.6L Engine (VIN 1 – RPO LB7) This bulletin is being issued to revise DTC P0540 in the Engine

Controls – 6.6L sub-section of the Service Manual. Please replace the current information in the Service Manual with the following information.

The diagnostic information and procedures for DTC P0540 have

been revised in the above application to reflect the use of a scan tool to operate the intake air heater (IAH) during the testing procedure. The operation of the IAH depends on variables that may not be within the technicians’ control. By using a scan tool to turn the IAH ON and OFF, you can consistently put the IAH in the mode desired for that step in the test.

Circuit Description The engine control module (ECM) uses an intake air heater (IAH) to

warm the incoming air for proper cylinder combustion. The ECM grounds the control coil of the IAH relay to energize the heater during cold operation. If the ECM detects voltage on the IAH circuit when the relay in commanded OFF, or incorrect voltage when the relay id commanded ON, a DTC will set.

Conditions for Running the DTC • The battery voltage is between 10-18 volts.

• The intake air temperature (IAT) is less than 23°C (73°F) with the engine running

OR • The coolant temperature is less than 49°C (121°F) with the

ignition ON, engine OFF for more than 3 seconds.

Conditions for Setting the DTC The heater line voltage is more than 8.1 volts with the relay OFF. OR The heating line voltage is between 3.8-8.1 volts with the ignition OFF. AND The heater line voltage is less than 0.5 volt below battery voltage with the ignition ON. OR The heater line voltage is less than 3.8 volts with the relay OFF. AND The reference line voltage is low with the relay OFF. Action Taken When the DTC Sets

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails; the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. Conditions for Clearing the MIL/DTC • The control module turns OFF the malfunction indicator lamp (MIL) after three consecutive ignition cycles that the diagnostic runs and does not fail. • A current DTC, Last Test Failed, clears when the diagnostic runs and passes. • A history DTC clears after 40 consecutive warm-up cycles if no failures are reported by this or any other emission related diagnostic. • Clear the MIL and DTC with a scan tool. Test Description The number below refers to the step number on the diagnostic table.

4. This step checks for battery voltage output from the IAH relay to the IAH.

Step Action Values Yes No

1 Did you perform the Diagnostic System Check-Engine Controls?

-

Go to Step 2

Go to Diagnostic

System Check-Engine

Controls

2 Is the DTC P0380 also set? - Go to DTC P0380

Go to Step 3

3

1. Turn OFF the ignition. 2. Turn ON the ignition, with the engine OFF. 3. Command the IAH ON and OFF with the scan

tool 4. Observe the IAH parameter with the scan tool

Does the scan tool display a voltage near the first specified value wit the IAH command ON and near the second specified value with the IAH commended OFF?

11-13 V,

0.0V

Go to step

9

Go to step 4

4

1. Turn ON the ignition, with the engine OFF. 2. Touch the supply stud of the IAH with a test

lamp connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

3. Command the IAH ON and OFF with the scan tool.

Does the test lamp illuminate with the IAH commanded ON, and turn OFF with the IAH commanded OFF.

-

Go to step

9

Go to step 5

5

1. Turn OFF the ignition. 2. Disconnect the IAH relay connector. Refer to

Intake Air Heater (IAH) Relay Replacement. 3. Turn ON the ignition, with the engine OFF. 4. Probe the IAH relay harness connector ignition 1

voltage circuit with a test lamp connected to a good ground.

Does the test lamp illuminate?

-

Go to step

6

Go to Step 10

6

1. Verify that the IAH relay harness is disconnected.

2. Turn ON the ignition, with the engine OFF. 3. Probe the IAH control circuit to the harness

connector with a test lamp connected to battery voltage.

4. Command the IAH ON and OFF with the scan tool.

Does the test lamp illuminate with the IAH commanded ON, and turn OFF with the IAH commanded OFF?

-

Go to Step 11

Go to Step 7

7

1. Verify that the IAH relay harness is disconnected.

2. Turn ON the ignition, with the engine OFF. 3. Probe the IAH control circuit with a DMM

connected to ground.

Does the voltage measure less than the specified value?

1 V

Go to step

8

Go to step 13

8

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

-

Go to

Step 16

Go to

Step 14

9

Test for an open or short to ground on one of IAH supply voltage circuits between the IAH supply stud and the ECM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find the correct condition?

-

Go to step 16

Go to Step 14

10

Repair the open or short to ground in the IAH ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?

-

Go to step

16

-

11

Test for poor connections at the IAH relay. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in the Wiring System. Did you find and correct the condition?

-

Go to step 16

Go to step 12

12

Replace the Intake air heater relay. Refer to Intake Air Heater (IAH) Relay Replacement. Did you complete the replacement?

-

Go to step

16

-

13

Repair the short to voltage on the relay control circuit. Refer to Wiring Repairs in Wiring Systems Did you complete the repair?

-

Go to step

16

-

14

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

-

Go to step 16

-

15

Replace the ECM. Refer to Engine Control Module (ECM) Replacement. Did you complete the replacement?

-

Go to step

16

-

16

1. Use a scan tool to clear the DTCs. 2. Turn OFF the ignition for 30 seconds. 3. Start the engine. 4. Operate the vehicle within the Conditions for

Running the DTC as specified in the supporting text.

Does the DTC run and pass?

-

Go to step 17

Go to step 2

17

With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed?

-

Go to Diagnostic

Trouble Code

(DTC) List

System OK

Service Bulletin

Bulletin No.: 02-07-30-032 Date: September 2002

Chevrolet/GMC

Information

Subject: Allison® Transmission Control Module Fast Learn Procedure Update Required after Transmission Repairs

Models: 2002-2003 Chevrolet Silverado 2002-2003 GMC Sierra with Allison® 1000 Series™ Automatic Transmission A new “FastLearn” procedure has been released for the Allison

1000 Series™ Transmission. The “FastLearn” procedure must be completed any the following vehicle repairs are performed:

• Transmission Replacement • Valve Body, Cleaning or Replacement • Solenoid A and/or B Replacement • Transmission Control Module Replacement • Transmission Control Module software or Calibration update The “FastLearn” procedure us a series of tests that are run to allow

the Transmission Control Module (TCM) to “Learn” (Adapt) to the characteristics of the clutch packs within the transmission. As each clutch packs data is learned, “FastLearn” stores the information in the adaptive cells for each clutch within the TCM. “FastLearn” will allow a repaired Allison 1000 Series™ transmission to be road tested after completion of the repair in as near –fully-adapted state as possible. This will allow the technician and customer to drive the vehicle in the adapted mode and reduce the number of technician and customer concerns after a transmission repair. The “FastLearn” procedure consists of four (4) steps (modes).

Park Mode While the transmission is in Park with the engine idling, FastLearn will

cycle through a series of tests where the C3 and C4 clutches are repeatedly applied to learn their clutch characteristics. During the C3 and C4 clutch apply/release procedure, FastLearn is able to characterize the A and B solenoid pressures corresponding to clutch return springs, and is also able to learn the volumes for C3

and C4 clutch packs. In addition, C5 clutch is repeatedly applied and released in Park to purge out air for later learning of its clutch volume.

Drive Mode Caution: While in Drive, if the Tech 2 loses communication, or

becomes disconnected, the vehicle may remain in Drive and could move forward if the wheels have not been securely blocked.

Once all of the Park test data have converged, the Tech 2®

instructs the driver to select Drive. Once Drive is selected, the TCM engages C1 clutch to obtain Drive and C1 clutch volume. The TCM repeats this test until the volume learned for C1 clutched has converged.

Reverse Mode Caution: While in Reverse, if the Tech 2 loses communication, or

becomes disconnected, the vehicle may remain in Reverse and could move backward if the wheels have not been securely blocked.

The Tech 2® will instruct the technician to select Reverse. When

Reverse is selected, the TCM engages C5 clutch to obtain reverse and learn the C5 clutch volume. The TCM repeats this test until the C5 clutch volume has converged.

After learning C1 and C5 clutch volume, FastLearn updates the adaptive volume data for all shifts with either C1 or C5 on-coming clutch.

C2 Lean Mode Following the Reverse Mode step, the Tech 2® exits “FastLearn”

and the only adaptive cells that remain to be learned are the adaptive volume data for the C2 clutch. The vehicle must be driven for this procedure to be completed. The requirements for this step require the vehicle be driven long enough and far enough at a steady throttle at a speed where at least three (3), 3-4 upshifts occur, on the same ignition cycle. The TCM learns the adaptive learn for the C2 clutch by overfilling the C2 clutch and then reducing the overfill until C2 is corrected, C2 clutch volume is learned and all special “FastLearn” actions are completely disabled.

“FastLearn” Procedure Important: The following conditions must be met before the

“FastLearn” procedure can be performed. • There should be no current or history DTC’s.

• The Neutral Start Back-up Switch must be operational and properly adjusted.

• All transmission vehicle speed sensors should be connected and functioning properly.

• The transmission fluid temperature should be between 40°C and 100°C (104°F and 212°F).

• The transmission line pressure must be within specified values. • The Transmission Converter Clutch (TCC) slip speed should be less

than 100 RPM at idle in park/neutral. • Block the drive wheels. • Apply the park brake. • Place the transfer case in “Two wheel Drive High” (if equipped). • Throttle at 0%, engine at warm engine idle speed. • Apply Service Brake during the Drive and Reverse Mode. Important: The Tech 2® software version must be 22.006, released

in August 2002, or newer. 1. Firmly apply the park brake. 2. Connect the Tech 2® to the Vehicle ALDL Connector. 3. Turn the ignition key ON with the engine off. 4. Power up the Tech 2® by pressing the power key. 5. Is software version 22.006, or newer displayed on the Tech 2®?

If not, you must go get it. If yes, press the enter key. 6. Select FO: Diagnostics. 7. Select: Model Year. 8. Select: Lt. Duty Truck. 9. Select FO: Powertrain. 10. Select: “The Proper Engine”. 11. Select: “Five Speed Automatic”. 12. Select: The proper Emission Level, California or Federal. 13. Select F2: Special Functions. 14. Select F1: Transmission Output Controls. 15. Press the up-arrow to select the: “Fast learn Adapt Process”,

Press Enter. 16. Follow the instructions displayed on the Tech 2. You will notice

the Transmission Fluid Temperature is displayed in a Bar graph at the top of the Tech 2 display screen.

17. When the Tech 2 states the Fast Learn has completed, Exit to the main menu.

18. Disconnect the Tech 2. 19. Drive the vehicle long enough and far enough at a steady

throttle at a speed where at least three (3), 3-4 upshifts occur, on the same ignition cycle.

The technician should then verify the operating characteristics of

the of the transmission and that transmission shift quality is acceptable before releasing the vehicle to the customer.

Service Bulletin

Bulletin No.: 02-01-38-007 Date: December 2002

Chevrolet/GMC

Technical

Subject: Poor A/C Performance – A/C Will Not Blow Cold Enough (Perform A/C System Checks) Models: 2003 Chevrolet Silverado 2003 GMC Sierra with 6.6L Diesel Engine (VIN 1 – RPO LB7) Condition: Some customers may comment on less than desirable A/C

performance, especially when ambient temperature is above 90°C (194°F).

Correction: If normal diagnostics do not lead to a correction, then perform the

following A/C system checks. 1. Re-calibrate the actuators. Refer to Recalibrating Actuators in

the HVAC System – Manual/Automatic sub-section of the Service Manual (SI Document ID # 904666).

2. Inspect the lower A/C condenser deflector for proper installation. The deflector should be positioned at the lower part of the condenser and extend forward into the top of the front bumper and below the two fresh air intake holes.

3. Check the engine cooling fan clutch for proper operation. Refer to Fan Clutch Diagnosis in the Engine Cooling sub-section of the Service Manual (SI Document ID #774320).

4. If the vehicle is equipped with a front license plate, inspect for proper installation. If the license plate bracket is installed upside down, it will block part of the two fresh air intake holes in the bumper. When the license plate bracket is installed correctly, the writing on the back of the bracket will be upside down.

5. Some improvements have been found by lowering the A/C charge from 0.82 kg (1.8 lbs) to 0.73 kg (1.6 lbs). When recovering the A/C charge, recovery must be pulled for at least 45 minutes.

6. Check the low pressure cycling switch for proper operation. The low pressure switch opens at 148 kPA (21.5 psi), which stops compressor operation and closes when the low side pressure reaches 276 kPA (40 psi). This enables the compressor to turn back on.

7. When performing the refrigerant system performance test, refer to the updated specification chart listed below.

A/C Performance Table – 6.6L Ambient Air Temperature

Relative Humidity

Service Port Pressure

Maximum Discharge

Air Temperature

Low Side High Side 13-18°C (55-65°F)

0-100% 198-328kPa (29-48 psi)

350-990 kPa (51-144 psi)

10°C (50°F)

Below 40% 292-450 kPa (42-65 psi)

560-1230 kPa (81-179 psi)

13°C (55°F) 19-24°C (66-75°F) Above 40% 294-553 kPa (43-

80psi) 710-1440 kPa (103-209 psi)

16°C (61°F)

Below 35% 346-523 kPa (50-76 psi)

1010-1560 kPa (147-226 psi)

16°C (61°F)

35-50% 397-593 kPa (58-86 psi)

1120-1650 kPa (163-240 psi)

18°C (64°F)

25-29°C (76-85°F)

Above 50% 436-733 kPa (63-106 psi)

1200-1820 kPa (174-264 psi)

20°C (68°F)

Below 30% 390-590 kPa (57-86 psi)

1370-1960 kPa (199-285 psi)

21°C (70°F)

30-50% 460-734 kPa (67-107 psi)

1450-2080 kPa (210-302 psi)

23°C (73°F)

30-35°C (86-95°F)

Above 50% 553-949 kPa (80-138 psi)

1570-2270 kPa (228-330 psi)

25°C (77°F)

Below 20%

407-584 kPa (59-85 psi)

1760-2330 kPa (255-338 psi)

25°C (77°F)

20-40% 479-778 kPa (70-113 psi)

1820-2460 kPa (264-357 psi)

27°C (81°F)

36-41°C (95-105°F)

Above 40% 622-971 kPa (90-141 psi)

1940-2590 kPa (282-376 psi)

29°C (84°F)

Below 20% 448-639 kPa (65-93 psi)

2180-2680 kPa (316-389 psi)

29°C (84°F) 42-46°C

(106-115°F)

Above 20% 544-874 kPa (79-127 psi)

2250-2820 kPa (327-409 psi)

31°C (88°F)

47-49°C (116-120°F)

Below 30% 599-874 kPa (79-116 psi)

2600-2970 kPa (377-431 psi)

32°C (90°F)

Service Bulletin

Bulletin No.: 02-06-04-058 Date: December 2002

Chevrolet/GMC

Technical

Subject: Service Engine Soon Lamp Illuminated, False DTCs P0181 and/or P0116 (Reprogram ECM)

Models: 2001-2002 Chevrolet Silverado 2500/3500 Series Pickup

Models 2001-2002 GMC Sierra 2500/3500 Series Pickup Models with 6.6L Duramax™ Diesel Engine Condition: Some customers may comment that the Service Engine Soon (SES)

Light is/was on. No abnormal driveability issues are known. Diagnostic Tips

The technician may find a Current or History DTC P0181 stored in the ECM. After the technician performs the diagnostics in SI and, if no trouble Is found, reflash the ECM.

Correction: DO NOT REPLACE THE ECM/PCM. 1. Re-program the ECM/PCM following normal SPS procedures (TIS

Version 8.0 released July 2002, or newer) 2. Clear all codes. 3. Disconnect the Tech 2 and return the vehicle to the customer.

Calibration Information Electronic calibration files are NOT available from GMSPO. Calibrations are available from Techline beginning with the TIS 2000

data release of version 8.0, released July 2002, or newer.

Service Bulletin

Bulletin No.: 02-06-01-036 Date: October 2002

Chevrolet/GMC

Service Manual Update

Subject: Revised Cylinder Head M12 Bolt Fastener Tightening Specifications

Models: 2001-2002 Chevrolet Silverado 2003 Chevrolet Kodiak 2001-2002 GMC Sierra 2003 GMC TopKick with 6.6L Duramax™ Diesel Engine (VIN 1 – RPO LB7) This bulletin is being issued to revise the fastener tightening

specification in the installation procedure for Cylinder Head Replacement – Left and Cylinder Head Replacement – Right and in the Fastener Tightening Specifications in the engine Mechanical – 6.6L sub-section of the Service Manual and the 2002 Engine Unit Repair Manual. Please replace the current information in the Service Manual/Engine Unit Repair Manual with the following information.

The following information has been updated within SI. If you are using a paper version of this Service Manual/Engine Unit Repair Manual, please make a reference to this bulletin on the affected page.

Cylinder Head Replacement (Silverado, Sierra, Kodiak,

TopKick) Step 5 of the Cylinder Head Replacement – Left and Cylinder Head

Replacement – Right has been revised as follows: Tighten the cylinder head bolts in the following steps using the

proper sequence. Tighten • Tighten the M12 bolts to 50 N•m (37 lb ft). • Tighten the M12 bolts to 80 N•m (59 lb ft). • Using the J 36660-A, tighten the M12 bolts 90 degrees. • Using the J 36660-A, tighten the M12 bolts to 75 degrees. • Tighten the M8 bolts to 25 N•m (18 lb ft).

Cylinder Head Installation (Engine Unit repair Manual) Step 3 of the Cylinder Head Installation – Left and Cylinder Head

Installation – Right has been revised as follows: Install the NEW M12 cylinder head bolts. Reuse the M8 bolts.

Tighten the M12 cylinder head bolts in three steps: Tighten • Tighten the M12 bolts to 50 N•m (37 lb ft). • Tighten the M12 bolts to 80 N•m (59 lb ft). • Using the J 36660-A, tighten the M12 bolts 90 degrees. • Using the J 36660-A, tighten the M12 bolts to 75 degrees. • Tighten the M8 cylinder heat bolts to 25 N•m (18 lb ft). Fastener Tightening Specifications (Silverado, Sierra, Engine

Unit Repair Manual) The fastener tightening specifications for the cylinder head M12

bolt has been revised as follows: Cylinder Head M12 Bolt

(Angular Tightening Method) 1st Step 50 N•m

1st Step 37 lb ft

2nd Step 80 N•m

2nd Step 59 lb ft

3rd Step 90 Degrees

4th Step 75 degrees

Service Bulletin

Bulletin No.: 02-08-42-005 Date: October 2002

Chevrolet/GMC

Technical

Subject: Snowplow Roof Beacon (Lamp) Inoperative (Install Bypass Harness)

Models: 2003 Chevrolet Silverado, Suburban, Tahoe 2003 GMC Sierra, Yukon, Yukon XL with Snow Plow Provision (RPO VYU) and Roof Mounted Lamp

Provisions (RPO TRW/5G4) Built Prior to September 16, 2002 Condition: Some customers may comment that the roof mounted snowplow

beacon (lamp) is inoperative. Cause: Vehicle may have been built without the required battery voltage

circuit #2340 in the IP harness. Correction: Install a bypass harness adding circuit #2340 to the IP harness using

the service procedure listed below. 1. Construct a bypass harness.

• Obtain standard stock 12 gauge red wire and cut to a length of 1000 mm (40 in). • Strip 5 mm (3/16 in) of insulation from each end of the wire. • Crimp the terminals, P/N 12110842, to each end of the wire. • Solder the crimps with rosen core solder.

2. Obtain a 7 mm (1/4 in) inside diameter vacuum tube or other equivalent hollow plastic tube approximately 152 to 203 mm (6-8 in) long. Apply an angle cut to one end of the tube.

3. Apply WD-40 lubricant to the outer area of tube, especially near the angle cut end.

4. From underhood, locate and untape the smaller pass-through grommet at the right side of the brake booster.

5. Inserting the “angle cut” lubed portion of the tube (outside to inside), slowly manipulate the plastic tube inside the nozzle of

the grommet, proceeding cautiously so as to not damage any existing wires.

6. Once the tube is through the grommet, insert one end of the bypass wire and push through the tube until the wire is through the grommet and past the inserted end of the tube.

7. Once the wire is through the grommet, the tube can be removed. Pull enough wire through the grommet to get to the IP relay block.

8. Re-tape harness at the grommet. 9. Route the wire underhood along the IP harness branch to the

underhood electrical center. 10. Remove the left fender upper brace. 11. Remove the underhood electrical center cover. 12. Push on the tab so that the electrical center can be rotated

exposing the underside. 13. Remove the IP 68-way (light gray) connector (C1) from the

electrical center. 14. Remove the TPA from the connector and install the terminal of

the new wire into cavity E11. 15. Reinstall the TPA, the connector, the electrical center and the

cover. 16. Carefully secure the wire to the IP harness with tape, ensuring

proper routing and clearance from sharp objects or pinch points.

17. Inside the vehicle, route the new wire to the IP relay block, securing as needed to the main IP harness.

18. Remove the IP relay block from it’s mounting bracket and remove the 68-way (light gray) connector (C1) from the IP.

19. Remove the TPA from the connector and install the terminal of the new wire into cavity D12.

20. Reinstall the TPA and connector onto the relay block; reinstall the relay block into the bracket.

Parts Information

Part Number Description Quantity 12110842 Terminal 2

The terminal is included in Packard Terminal Repair Kit J 38125-A or

available from GMSPO.

Service Bulletin

Bulletin No.: 02-06-04-049 Date: September 2002

Chevrolet/GMC

Service Manual Update

Subject: Revised DTC P0201-P0208 Models: 2001-2002 Chevrolet Silverado Pickup Models 2001-2002 GMC Sierra Pickup Models with 6.6L Duramax™ Diesel Engine (VIN 1 – RPO LB7) This bulletin is being issued to revise DTC P0201-P0208 in the Engine

Controls – 6.6L sub-section of the Service Manual. Please replace the current information in the Service Manual with the following information.

The following information has been updated within SI. If you are using a paper version of this Service Manual, please make a reference to this bulletin on the affected page.

The diagnostic information and procedures for DTC P0201-P0208 have been revised in the above applications to reflect the change in the tool used to diagnose the circuit faults. Using a test lamp may not find wiring insulation problems that will allow the high voltage to go to ground. Using a DMM will find any circuit insulation problems.

Circuit Description The fuel injection control module (FICM) supplies high voltage to

each fuel injector on the injector supply voltage circuits. The FICM enables each fuel injector by grounding the command circuit between the FICM and the fuel injector. The FICM monitors the status of the injector supply voltage circuits and the fuel injector command circuits. When a fuel injector circuit condition is detected by the FICM, all of the fuel injectors on the affected injector supply voltage circuit will be disabled. If a circuit condition is detected on a fuel injector circuit for cylinders 1, 4, 6, or 7, DTCs P0201, P0204, P0206, P0207 will set, along with DTC P1261. If a circuit condition is detected on a fuel injector circuit for cylinders 2, 3, 5, or 8, DTCs P0202, P0203, P0205, P0208 will set, along with DTC P1262.

Conditions for Running the DTC • DTCs U1800, and U2104 are not set. • The engine is running. • The charging system voltage is between 6-18 volts. Conditions for Setting the DTC • The FICM detects an incorrect current on a fuel injector circuit. • The condition exists for less than 1 second. Action Taken When the DTC Sets • The control module illuminates the malfunction indicator lamp

(MIL) when the diagnostic runs and fails. • The control module records the operating conditions at the time

the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

• The control module disables the set of fuel injectors that have a concern.

Conditions for Clearing the MIL/DTC • The control module turns OFF the malfunction indicator lamp

(MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A history DTC clears after 40 consecutive warm-up cycles if no failures are reported by this or any other emission related diagnostic.

• Clear the MIL and the DTC with a scan tool. Test Description The numbers below refer to the step numbers on the diagnostic

table. 2. This step verifies that the condition is not intermittent.

4. This step determines which set of fuel injectors the circuit condition is affecting. If DTC P1261 is set, then a condition exists on cylinders 2, 3, 5, or 8.

5. This step tests if a ground is constantly being applied to the fuel injectors.

6. This step isolates which circuit is causing the condition. If the test lamp turns OFF when a multi-way connector is disconnected, test the affected circuits for a short to ground.

7. This step test for an open circuit. If the DMM displays OL on all of the fuel injector circuits, the ignition voltage circuit is open.

8. This step tests for an open circuit. If the DMM displays OL on one of the fuel injector circuits, the fuel injector command circuit is open.

9. This step tests for excessive resistance in a fuel injector circuit. 10. This step is testing for a short between the ignition feed circuit

and the fuel injector command circuit. If the resistance of the circuit is less than 0.3 ohms, test for a short between the circuits. If a short cannot be found, the fuel injector may be the cause of the condition. The normal fuel injector resistance is between 0.3-0.4 ohms.

11. This step tests for a short to voltage on a fuel injector circuit. If the DMM displays battery voltage, a short to voltage is the cause of the condition.

12. This step isolates which circuit is causing the condition. If the DMM display changes to 0 volts when a multi-way connector is disconnected, test the affected circuits for a short to voltage.

13. This step tests if a ground is constantly being applied to the fuel injectors.

14. This step isolates which circuit is causing the condition. If the DMM displays OL when a multi-way connector is disconnected, test the affected circuits for a short to ground.

15. This step tests for an open circuit. If the DMM displays OL on all of the fuel injector circuits, the ignition voltage circuit is open.

16. This step tests for an open circuit. If the DMM displays OL on one of the fuel injector circuits, the fuel injector command circuit is open.

17. This step tests for excessive resistance in a fuel injector circuit. 18. This step is testing for a short between the ignition feed circuit,

and the fuel injector command circuit. If the resistance of the circuits is less than 0.3Ω, test for a short between the circuits. If a short cannot be found, the fuel injector may be the cause of the condition. The normal fuel injector resistance is between 0.3-0.4 ohms.

19. This step tests for a short to voltage on a fuel injector circuit. If the DMM displays battery voltage, a short to voltage is the cause of the condition.

20. This step isolates which circuit is causing the condition. If the DMM display changes to 0 volts when a multi-way connector is disconnected, test the affected circuits for a short to voltage.

Step Action Values Yes No Schematic Reference: Engine Control Schematic. Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views.

1 Did you perform the Diagnostic System Check –Engine Controls?

- Go to Step 2

Go to Diagnostic

System Check-Engine

Controls 2 Observe the DTC information with a scan

tool. Are DTCs P0201, P0204, P0206, P0207, or P0202, P0203, P0205, O0208 set?

-

Go to Step 4

Go to Step 3

3

1. Observe the Freeze Frame/Failure Records for this DTC.

2. Turn OFF the ignition for 30 seconds. 3. Start the engine. 4. Operate the vehicle within the

Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

-

Go to Step 4

Go to Intermittent Conditions

4 Is DTC P1261 also set? - Go to Step 13

Go to Step 5

5

Caution: Refer to High Voltage Caution in Cautions and Notices. Important: Refer to Engine Controls Components Views for fuel injector locations. Failure to identify the correct cylinder will result in misdiagnosis. 1. Turn OFF the ignition. 2. Disconnect the FICM. 3. Measure the resistance between the

injector supply voltage circuit for cylinders 2, 3, 5, and 8 and ground with a DMM.

Does the DMM display OL?

-

Go to Step 7

Go to Step 6

6

Disconnect each multi-way harness connector of the fuel injectors one at a time, while monitoring the DMM. Does the DMM display OL when any of the fuel injector harness connectors are disconnected?

-

Go to Step 21

Go to Step 34

7

Important: The DMM and test leads must be calibrated to 0 ohms in order to prevent misdiagnosis. Use the J 39200 DMM to perform this test. Refer to the DMM User Manual for calibration procedure. Measure the resistance between the ignition voltage circuit and the injector command circuits for cylinders 2, 3, 5, and 8 with a DMM Does the DMM display OL for all of the circuits?

-

Go to Step 35

Go to Step 8

8 Does the DMM display OL for any of the circuits?

- Go to Step 23

Go to Step 9

9

Does the DMM display a resistance above the specified value for any fuel injector circuit?

0.8Ω

Go to Step

26

Go to

Step 10

10 Does the DMM display a resistance below the specified value for any fuel injector circuit?

0.3Ω

Go to Step

28

Go to

Step 11

11

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

2. Probe the ignition voltage circuit for cylinders 2, 3, 5 and 8, with a DMM connected to ground.

Does the DMM display battery voltage?

-

Go to Step 12

Go to Step 29

12

Disconnect each multi-way harness connector of the fuel injectors one at a time, while monitoring the DMM. Does the DMM display the specified voltage when any of the fuel injector harness connectors are disconnected?

0 V

Go to Step 32

Go to Step 31

13

Caution: Refer to High Voltage Caution in Cautions and Notices. Important: Refer to Engine Controls Component Views for fuel injector locations. Failure to identify the correct cylinder will result in misdiagnosis. 1. Turn OFF the ignition. 2. Disconnect the FICM. 3. Measure the resistance between the

injector supply voltage circuit for cylinders 1, 4, 6, and 7 and ground with a DMM.

Does the DMM display OL?

-

Go to Step 15

Go to Step 14

14

Disconnect each multi-way harness connector of the fuel injectors one at a time, while monitoring the DMM. Does the DMM indicate OL when any of the fuel injector harness connectors are disconnected?

-

Go to Step 21

Go to Step 34

15

Important: The DMM and test leads must be calibrated to 0 ohms in order to prevent misdiagnosis. Refer to the DMM User Manual for calibration procedure. Measure the resistance between the injector supply voltage circuit and the injector command circuits for cylinders 1, 4, 6, and 7 with a DMM. Does the DMM display OL for all of the circuits?

-

Go to Step 35

Go to Step16

16 Does the DMM display OL for any of the circuits?

- Go to Step 23

Go to Step 17

17

Does the DMM display a resistance above the specified value for any fuel injector circuit?

0.8Ω

Go to Step

26

Go to

Step 18

18 Does the DMM display a resistance below the specified value for any fuel injector circuit?

0.3Ω

Go to Step

28

Go to

Step 19

19

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

2. Probe the injector supply voltage circuit for cylinders 1, 4, 6 and 7, with a DMM connected ground?

Does the DMM display battery voltage?

-

Go to Step 20

Go to Step 29

20

Disconnect each multi-way harness connector of the fuel injectors one at a time, while monitoring the DMM. Does the DMM display the specified voltage when any of the fuel injector harness connectors are disconnected?

0 V

Go to Step 32

Go to Step 31

21

Measure the resistance from the fuel injector command circuit to ground between the FICM and the multi-way connector for the cylinder that caused the DMM to display OL. Does the DMM display continuity?

-

Go to Step 33

Go to Step 22

22

Test both the fuel injector circuits, of the isolated cylinder, between the fuel injector and the multi-way connector for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in wiring Systems. Did you find and correct the condition?

-

Go to Step 38

Go to Step 30

23

1. Disconnect the multi-way connector of the fuel injector that displayed OL.

2. Test the command circuit of the fuel injector, between the FICM and the multi-way connector, for the following:

• An open circuit • A poor connection 3. Refer to Connector Repairs or Wiring

Repairs in Wiring Systems. Did you find and correct the condition?

-

Go to Step 38

Go to Step 24

24

1. Test the ignition voltage circuit of the fuel injector, between the multi-way connector and the splice, for the following: • An open Circuit • A poor connection

2. Refer to Connector Repairs or Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

-

Go to Step 38

Go to Step 25

25

Test both of the fuel injector circuits between the fuel injector and the multi-way connector for an open. Refer to Testing and Continuity and Wiring Repairs in wiring Systems. Did you find and correct the condition?

-

Go to Step 38

Go to Step 30

26

1. Disconnect the multi-way connector for the circuit with high resistance.

2. Test for the following conditions: • Excessive resistance in the fuel injector circuits between the FICM and the multi-way connector • Poor connections at the multi-way connector of the fuel injector

3. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

-

Go to Step 38

Go to Step 27

27

Test both of the fuel injector circuits between the fuel injector and the multi-way connector for high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition?

-

Go to Step 38

Go to Step 30

28

Test for a short between the injector supply voltage ignition circuit and the fuel injector command circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

-

Go to Step

38

Go to

Step 36

29

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

-

Go to Step 38

Go to Step 37

30

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

-

Go to Step 38

Go to Step 36

31

Repair the short to voltage in the injector supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?

-

Go to Step

38

-

32

Repair the short to voltage in the fuel injector command circuit that turned OFF the test lamp. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?

-

Go to Step 38

-

33

Repair the short to ground in the fuel injector command circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?

-

Go to Step

38

-

34

Repair the short to ground in the injector supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?

-

Go to Step

38

-

35

Repair the open in the injector supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?

-

Go to Step

38

-

36

Important: Refer to Engine Controls Component Views for fuel injector locations. Replace the appropriate fuel injector. Refer to Fuel Injector Replacement. Did you complete the replacement?

-

Go to Step 38

-

37

Replace the FICM. Refer to Fuel Injection Control Module Replacement. Did you complete the replacement?

-

Go to Step

38

-

38

1. Clear the DTCs with a scan tool. 2. Turn OFF the ignition for 30 seconds. 3. Start the engine. 4. Operate the vehicle within the

Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

-

Go to Step 2

-

39

Observe the Capture Info with a scan tool. Are there any DTCs that have not been

diagnosed

-

Go to Diagnostic

Trouble Code

(DTC) List

-