CAMPAIGN:POOR THROTTLE RESPONSE, STALLING, MISFIRE. GMC Truck GMC K Pickup

SUBJECT: POOR THROTTLE RESPONSE, STALLING, MISFIRE, POOR COLD OR HOT START, EXTENDED CRANK HOT START THEN STALL HOT

Models: 1994 Chevrolet and GMC C/K Trucks and G Vans with 6.5L Diesel Engine (RPO's L65, L56 and L49 with Automatic and/or Manual Transmission)

TO: ALL GENERAL MOTORS DEALERS

General Motors of Canada Limited has determined that certain 1994 Chevrolet and GMC C/K Trucks and G Vans may experience poor throttle response, stalling, misfire, poor cold or hot starting, extended cranking of the starter with a hot engine, and/or your vehicle will start and then stall when the engine is hot. Vehicles with manual transmissions may also experience deceleration stall and poor acceleration performance.

0 Poor cold starting includes an extended crank time (more than 4 seconds at temperatures of 0 degrees Fahrenheit (-18 degrees Celsius) and above), rough idle, white smoke and/or start then stall. A cold start is defined as starting the engine after shut down for more than three hours.

0 No start or extended cranking of the starter with a hot engine, starting then stalling when the engine is hot, is defined as starting the engine within three hours of shutdown (extended cranking time with a hot engine is defined as more than 4 seconds cranking time).

To correct these conditions, involved vehicles will be updated with service parts and a PCM PROM, described later in this bulletin.

VEHICLES INVOLVED:

Involved are certain 1994 Chevrolet and GMC C/K Trucks and G Vans built within the following VIN breakpoints:

GMC

Year Model Plant Plant Code From Through

1994 Suburban w/L65 Janesville J SOP RJ766442 1994 Crew Cab w/L65 Janesville J SOP RJ766442 1994 Yukon w/L56 Janesville J SOP RJ764990 1994 Chassis Cab w/L65 Janesville J SOP RJ524402 1994 Pickup w/L65 Pontiac East E SOP RE560831 1994 Pickup w/L56 Pontiac East E SOP RE560802 1994 Pickup w/L49 Pontiac East E SOP RE560778 1994 Pickup w/L56 Oshawa 1 SOP R1585416 1994 Pickup w/L49 Oshawa 1 SOP R1585335 1994 Van w/L49 Flint H SOP EOP

CHEVROLET

Year Model Plant Plant Code From Through

1994 Suburban w/L65 Janesville J SOP RJ432698 1994 Crew Cab w/L65 Janesville J SOP RJ432698 1994 Blazer w/L56 Janesville J SOP RJ433173 1994 Chassis Cab w/L65 Janesville J SOP RJ115874 1994 Pickup w/L65 Pontiac East E SOP RE294189 1994 Pickup w/L56 Pontiac East E SOP RE294131 1994 Pickup w/L49 Pontiac East E SOP RE294185 1994 Pickup w/L56 Oshawa 1 SOP R1310457 1994 Pickup w/L49 Oshawa 1 SOP R1310440 1994 Van w/L49 Flint H SOP EOP

NOTE: PLEASE CHECK DCS SCREEN 45 OR YOUR V.I.N. LISTING BEFORE PERFORMING CAMPAIGN TO ENSURE THAT THE VEHICLE IS AFFECTED. ONLY AFFECTED VIN'S WILL BE PAID.

All affected vehicles have been identified by the VIN listing provided to involved dealers with this bulletin. Any dealer not receiving a listing was not shipped any of the affected vehicles.

DEALER CAMPAIGN RESPONSIBILITY:

All unsold new vehicles in dealer's possession and subject to this campaign must be held and inspected/repaired per the Service Procedure of this Campaign Bulletin before owners take possession of these vehicles.

Dealers are to perform this campaign on all involved vehicles at no charge to owners, regardless of kilometers traveled, age of vehicle, or ownership, from this time forward.

Owners of vehicles recently sold from your new vehicle inventory with no owner indicated on the dealer listing, are to be contacted by the dealer, and arrangements made to make the required correction according to instructions contained in this bulletin. This could be done by mailing to such owners a copy of the owner letter accompanying this bulletin. Campaign follow-up cards should not be used for this purpose, since the owner may not as yet have received the notification letter.

In summary, whenever a vehicle subject to this campaign is taken into your new or used vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle.

CAMPAIGN PROCEDURE

Refer to Section 4 of the Service Policies and Procedures Manual for the detailed procedure on handling Product Campaigns. Dealers are requested to complete the campaign on all transfers as soon as possible.

OWNERS NOTIFICATION

All owners of record at the time of campaign release are shown on the attached computer listing and have been notified by first class mail from General Motors (see copy of owner letter included with this bulletin). The listings provided are for campaign activity only and should not be used for any other purpose. In addition, the owners will also be provided a pamphlet entitled "How To Get The Most From Your EFI Diesel Truck."

PARTS INFORMATION:

NOTE: Some vehicles may already have all or some of the latest parts available. Replacement of these parts is not necessary

Parts required to complete this campaign are as follows and should be ordered through regular channels:

Part Number Description Quantity/Vehicle ----------- ----------- ---------------- NPN Injection Pump (Blue Tag) 12553327 Filter Harness 1 15985629 Start Procedure Label - English 1 52367143 Start Procedure Label - French 1 See Chart* PROM 1

* To order correct PROM for vehicle, check current Scan I.D. with Tech 1, then cross reference the Scan I.D. using the chart listings on Pages 4 and 5.

NOTE: Injection pumps are to be exchanged through Stanadyne. DO NOT order from GMSPO (Replace injection pumps with black color I.D. tags only. Do not replace blue tag pumps). Injection pumps on new unsold vehicles must be replaced with new injection pumps. Notify your Stanadyne Dealer when an exchange pump is for a new unsold vehicle.

NOTE: A Technical Assistance Center case is required to obtain an exchange pump. Injection pumps are currently available through a Stanadyne Dealer (see GM Corporate Service Bulletin 376302, dated October 1994, for Stanadyne Dealer near you).

1994 L56 (VIN S) WITH AUTOMATIC TRANSMISSION

New B/C Body Current New PROM (PROM New PROM Style/Series Scan ID P/N Labels) ID (Scan Tool) --------------------------------------------------------------------------- Pickup C1 -2 6925 16211620 BMXZ 1605 Pickup K1-K2, 6935 16211623 BMYA 1615 Yukon/Blazer K1 Pickup C1-2 3285,7415 16210063 BMRK 9935 Pickup K1-K2, 3295,7425 16210068 BMRL 9945 Yukon/Blazer K1

1994 L65 (VIN F) WITH AUTOMATIC TRANSMISSION

HD Chassis 6895,3305,7385 16210156 BMSF 0155 Cab C3/C5B* BPBP 7135

Pickup 6945,3345,7375 16210072 BMRM 9955 C/K2-3 BPBR 7145 Chassis Cab C/K3

Suburban 3325,7345 16210082 BMRP 9975 C/K2 BPBT 7165

HD Chassis 3355,7335 16210078 BMRN 9965 Cab C3/C5B* BPBS 7155

Ambulance 3685 16210093 BMRT 0005 C/K 2-3 BPBW 7185

HD 3695 16210097 BMRU 0015 Ambulance BPBX 7195 C3/C5B*

Pickup 6465 16210217 BMSW 0275 C/K2-3 BPBK 7095 Chassis Cab C/K3

Suburban 6475 16210226 BMSY 0295 C/K2 BPBM 7115

HD Chassis 5755 61210220 BMSX 0285 Cab 3/C5B* BPBL 7105

1994 L65 (VIN F) WITH MANUAL TRANSMISSION

HD Chassis 6915,2235,3315, 16215263 BNTH 5185 Cab C3/C5B* 7405,0175

HD Chassis 8605,0185 16215266 BNTJ 5195 Cab C3/C5B*

Pickup 3365,7355,9985 16215253 BNTB 5145 C/K2-3

Chassis Cab 3375,7365,9995 16215256 BNTC 5155 C3/C5B*

HD Chassis 8595,0025 16215258 BNTD 5165 Cab C3/C5B*

* C5B: 15,000 LB GVW

1994 L49 (VIN P) WITH AUTOMATIC TRANSMISSION

New B/C Body Current New PROM (PROM New PROM Style/Series Scan ID P/N Labels) ID (Scan Tool) ---------------------------------------------------------------------------- Van G2 6835,3215,7435 16210182 BMSL 0195 BPBY 7205 Van G2 6845,3225,7445 16210187 BMSM 0205 BPBZ 7215 Pickup C1 6855,3235,7455 16210190 BMSN 0215 BPCA 7225 Pickup C1 6865,3245,7465 16210196 BMSP 0225 BPCB 7235 Pickup 6875,3255,7475 16210199 BMSR 0235 C2, K1-2 BPCC 7245

Pickup 6885,3265,7485 16210203 BMSS 0245 C2, K1-2 BPCD 7255

1994 L49 (VIN P) WITH MANUAL TRANSMISSION

Pickup C2, 6825,3205, 16215271 BNTP 5245 K1-2 7505,0265

PARTS AND LABOUR CLAIM INFORMATION:

Credit for the campaign work performed will be paid upon receipt of a properly completed campaign claim card or DCS transmission in accordance with the following:

Repair Code Description Time Allowance ----------- ----------- -------------- 6A Inspect Vehicle for Updated Parts 0.3 hrs. (PROM - Visor Label - Optic Filter - Injection Pump)

Engine Support Systems Diagnostic Checks 1.8 hrs. All Vehicles - Includes All Diagnostics Outlined In Attachments 1 Through 8)

PROM Replace (C/K/G) 0.3 hrs. Install Optic Sensor Filter 0.3 hrs. Install Visor Start Procedure Label 0.2 hrs. Air Filter Check Or Replace (If Necessary) 0.2 hrs. Fuel Filter Replace (If Necessary) 0.3 hrs.

Injection Pump Replace C/K without A/C 3.0 hrs. C/K with A/C 3.1 hrs. G Van without A/C 3.6 hrs. G Van with A/C 3.8 hrs.

Time allowance includes 0.1 hour for dealer administrative detail associated with this campaign. Parts credit will be based on dealer net plus 40% to cover parts handling.

SERVICE PROCEDURE

NOTE: A video tape providing a detail description of the repair procedure will be sent to all dealers the week of November 14, 1994.

It is very important that the video is viewed and that this bulletin is read and understood by all technicians prior to servicing a vehicle.

The following checks must be performed ON ALL VEHICLES to qualify the engine support systems. A diagnostic check sheet (Attachment 1) has been provided to assist in this process, and must be attached to the repair order. (This diagnostic check sheet should be reproduced locally.)

1. Check PROM ID using Tech 1. See Parts Information Section of this bulletin for ordering replacement PROM. If the new PROM is currently in the truck, do not replace. Check color of injection pump I.D. tag.

2. Check for diagnostic trouble codes (DTCs), both history and current. Use the 1994 Diesel Service Manual Supplement for diagnosis and correction. Clear all current and history DTCs before proceeding.

3. Check wiring connections at batteries, relay center, engine grounds and wiring grounds (Attachment 2) for secure and complete attachment.

4. Check air filter, clean or replace as necessary.

5. Check cold cranking RPM, spec: 100 RPM cold engine. Remove the fuel solenoid fuse from the fuse block located under the instrument panel to prevent the vehicle from starting. Crank the engine. Use the Tech 1 to view the engine cranking speed. The cold start reading should be at least 94 RPM on the Tech 1. Your Tech 1 must have the April 1994 or later Mass Storage Cartridge update to use this procedure. (For alternate method, See Attachment 3).

6. Check fuel supply system pressure, spec: 3 psi minimum at idle (Attachments 4 and 5).

7. Check glow plugs (Attachment 6).

8. Check for air in fuel system (see Attachment 8) for procedure.

9. If the engine is equipped with a blue label pump, relearn the TDC offset If the relearned value is between +.75 and -1.75 continue to the next step. If the value is not between +.75 and -1.75, reset pump timing following procedure shown in Attachment 9.

Once above procedures have been completed, install service parts which include, a visor label (engine start procedure), electronic filter harness (see Attachment 7) and a blue tag injection pump (if not already equipped). Install replacement PROM, using the Parts Information chart on Pages 4 and 5.

NOTE: Injection pumps are to be exchanged through Stanadyne. DO NOT order from GMSPO. (TAC case is required)

NOTE: If a blue tag injection pump was required, set timing using the procedure shown in Attachment 9.

10. Check the fuel rate at idle using Tech 1 (maximum spec. 13mm manual transmission or 15mm for automatic transmission). If out of specification, check fuel quality with a hydrometer (J34352). Refer to appropriate Service Manual for procedure and empty fuel system and refill with known good fuel if required.

11. Install Campaign Identification Label.

NOTE: IF OWNERS' CONCERN WAS HOT START OR EXTENDED CRANK HOT OF MORE THAN 4 SECONDS BEFORE STARTING, CONTINUE WITH THE FOLLOWING DIAGNOSIS.

1. Block the radiator and bumper holes, operate the engine with A/C off at 3400 RPM in neutral until coolant temperature reaches 220 degrees Fahrenheit (105 degrees Celsius) as indicated on the Tech 1, or stabilizes at a lower number.

2. Shut off engine and let the vehicle hot soak for 20-25 minutes.

3. Using a timer that accurately reads "seconds" record crank time.

4. If crank time exceeds 4 seconds check cranking speed, spec: 170-180 RPM, use the Tech 1 with the April 1994 or later software update or the Service Manual procedure to check the engine cranking speed. Hot cranking speed displayed by the Tech 1 should be a minimum of 169 RPM. Realize that the Tech 1 only reads in increments of 18.75 RPM. This is why the 169 RPM reading is lower than the Service Manual specification of 180. (For alternate method, See Attachment 3).

5. If crank speed is within specification and crank time exceeds 4 seconds, please contact Technical Assistance Center. They may be able to offer special help on particular situations.

INSTALLATION OF CAMPAIGN IDENTIFICATION LABEL

Clean surface of radiator upper mounting panel and apply a Campaign Identification Label. Make sure the correct campaign number is inserted on the label. This will indicate that the campaign has been completed.

Dear General Motors Customer:

Your complete satisfaction with your 1994 Truck or Van, equipped with a 6.5L Electronic Fuel Injection (EFI) Diesel Engine, is most important to General Motors. We want your 6.5L diesel to satisfy all your driving needs and wish to inform you that enhancements are available to improve your engine's driveability.

The 1994 6.5L EFI Diesel Engine in your Truck or Van is equipped with an Electronic Fuel Injection pump which is controlled by a powertrain control module (or computer). CERTAIN Trucks or Vans may exhibit some driveability concerns such as poor throttle response, stalling, misfire, poor hot or cold starting, extended cranking of a hot engine, or stalling after start. Trucks or Vans equipped with manual transmissions may exhibit poor acceleration from start characteristics or may stall during deceleration. To address these concerns, your GM dealer can install some recently developed enhancements which will improve the overall driving pleasure of your vehicle. These enhancements will be installed at no charge to you.

Instructions for performing this service have been sent to your GM dealer. Please contact your dealer to arrange a convenient service appointment. Please be prepared to describe the specific concern or symptom your vehicle exhibits. This will assist the dealer in accurately assessing the situation. Since some of the required parts are unique to your specific vehicle, a short first visit to the dealer may be necessary to determine the appropriate parts needed for your vehicle. On the second visit, the new parts will be installed and may require between 1 to 6 hours to install, depending on the repairs required.

We have also enclosed a brochure which describes some of the features of the 6.5L Diesel Engine and how it differs from diesel engines that utilize mechanical injection systems. Please take the time to read this important information.

This letter identifies your vehicle. Presentation of this letter to your dealer will assist their Service personnel in completing the necessary correction to your vehicle in the shortest possible time.

We sincerely regret the inconvenience or concern this situation may cause you. We have taken this action to ensure your General Motors Truck or Van provides years of pleasurable driving experience.

Customer Support Department General Motors of Canada Limited

Object Number: 76754 Size: FS

Object Number: 85128 Size: FS

Object Number: 79873 Size: FS

Object Number: 84010 Size: FS

Object Number: 81092 Size: FS

Object Number: 78764 Size: FS

Object Number: 78763 Size: FS

Object Number: 79872 Size: FS

Object Number: 81091 Size: FS

Object Number: 78762 Size: FS

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.