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 GMC C/K TRUCKS AND G VANS WITH 6.5L DIESEL ENGINE (RPO'S L65, L56 AND L49 WITH AUTOMATIC AND/OR MANUAL TRANSMISSION)

THIS BULLETIN CANCELS AND REPLACES 94-C-57 ISSUED OCTOBER 1994. DESTROY ALL COPIES OF 94-C-57. REVISIONS HAVE BEEN MADE TO THE SERVICE PROCEDURES, WARRANTY INFORMATION, AND THE TIMING PROCEDURE. ALL REVISIONS ARE DISTINGUISHED BY SHADED BOXES.

General Motors has determined that CERTAIN 1994 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 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 condition, involved vehicles will be updated with a service parts kit and a PCM PROM.

VEHICLES INVOLVED

Involved are CERTAIN 1994 GMC C/K trucks and G vans built within the following VIN breakpoints:

Model Year Plant From Through

Suburban w/L65 1994 Janesville SOP 1GKGC26F1RJ766442 Yukon w/L56 1994 Janesville SOP 1GKEK18S2RJ764990 Pickup w/L65 1994 Janesville SOP 1GDKC34F4RJ524402 Pickup w/L65 1994 Pontiac East SOP 1GTGC29F1RE560831 Pickup w/L56 1994 Pontiac East SOP 1GTFC24S5RE560802 Pickup w/L49 1994 Pontiac East SOP 1GTFC24P7RE560778 Pickup w/L56 1994 Oshawa SOP 2GTEK19S0R1585416 Pickup w/L49 1994 Oshawa SOP 2GTEK19P6RI585335 Van w/L49 1994 Flint SOP EOP

The specific vehicles involved in this campaign have been identified by Vehicle Identification Number (VIN) Computer Listings. These listings are furnished to all involved dealers with the campaign bulletin. Dealers should confirm vehicle eligibility through VISS (Vehicle Information Service System) or SERVICENET prior to beginning campaign repairs.

DEALER CAMPAIGN RESPONSIBILITY

All unsold vehicles in dealers' 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 service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward.

Owners of vehicles recently sold from your vehicle inventory are to be contacted by the dealer and arrangements made to make the required correction according to instructions contained in this bulletin.

In summary, whenever a vehicle subject to this campaign enters your 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.

If the name and address of the owner of an involved vehicle was unavailable to GMC Truck Division at the time of campaign initiation, the dealer must determine the owner's name and address from the dealership sales records. Please provide this information directly on the second copy of the listing next to the applicable VIN so that our records may be updated and the appropriate notification mailed to the owner. This second copy should then be submitted to the address listed below in the previously supplied yellow campaign envelopes.

General Motors Corporation 101 Union Street Plymouth. Michigan 48170

OWNER NOTIFICATION

Owners will be notified of this campaign on their vehicles by GMC Truck Division (see copy of owner letter included with this bulletin). in addition, the owners will also be provided a pamphlet entitled "How To Get The Most From Your EFI Diesel Truck". A listing of owner names and addresses has been furnished to the involved dealers to enable dealers to follow up with owners involved in this campaign. This listing may contain owner names and addresses obtained from State Motor vehicle Registration records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to this campaign.

SERVICE PROCEDURE

The following checks must be performed 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.

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 for secure and complete attachment (Attachment 2).

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

5. Check cold cranking RPM, spec: 100 RPM cold engine (Attachment 3).

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

7. Check glow plugs (Attachment 5).

Once above procedures have been completed, install service kit which contains a visor label (engine starting procedure), electronic filter harness, and two stage housing pressure regulator (See Attachment 6 and 7 for installation procedure). Install replacement PROM, using the Parts Information Section below.

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

9. Relearn the TDC Offset. If the relearned value is between +0.75 and -1.75, continue to the next step. If the value is not between +0.75 and -1.75, reset pump timing following the procedure shown in Attachment 9.

10. Check the fuel rate at idle using Tech 1 (maximum spec. 13mm manual transmission or 15 mm 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 source if required.

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

11. 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 as indicated on the Tech 1, or

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

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

14. If crank time exceeds 4 seconds check cranking speed, spec: 170-180 RPM (Attachment 3).

15. If crank speed is within specification and crank time exceeds 4 seconds replace the injection pump.

NOTE: Injection pumps are to be exchanged through Stanadyne. DO NOT order from GMSPO.

16. Change engine oil, filter and lubricate chassis.

17. Install Campaign Identification Label.

PARTS INFORMATION

Parts are to be obtained from General Motors Service Parts operation (GMSPO). To ensure parts are obtained as soon as possible, order them from GMSPO on a C.I.O. order with no special instruction code but order under an advise code (2).

Parts are available.

NOTE: Injection pumps are to be exchanged through Stanadyne. DO NOT order from GMSPO.

Injection pumps are currently available through a Stanadyne Dealer (see GM Corporate Service Bulletin 376302, dated September 1993, for Stanadyne Dealer near you.)

NOTE: A technical assistance case is not required to obtain an exchange pump.

Part Number Description Quantity ----------- ----------- -------- 12553873 Service Kit 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 below.

All PROMs listed below provide 1068 RPM fast idle upon request when properly modified.

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 K1

Pickup C1-2 3285,7415 16210063 BMRK 9935

Pickup K1-2, 3295,7425 16210068 BMRL 9945 Yukon K1

1994 L65 (VIN F) WITH AUTOMATIC TRANSMISSION

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

Pickup 3735.7325 16210072 BMRM 9955 C/K2-3, Chassis Cab C/K3

Suburban 3325,7345 16210082 BMPP 9975 C/K2

HD Chassis 3355,7335 16210078 BMFN 9965 Cab C3/C5B*

Motorhome P3 1025 16211628 BMYB 1625

**Ambulance 3685 16210093 BMRT 0005 C/K 2-3

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

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

Suburban 6475 16210226 BMSY 0295 C/K2

HD Chassis 5755 16210220 BMSX 0285 Cab C3/C5B*

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

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

** These PROMs provide 1360 RPM fast idle upon request, when properly modified.

1994 L49 (VIN P) WITH AUTOMATIC TRANSMISSION

Pickup C1 6855,3235.7455 16210190 BMSN 0215

Pickup C1 6865,3245,7465 16210196 BMSP 0225

Pickup 68 75,3255,7475 16210199 BMSR 0235 C2, K1-2

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

1994 L49 (VIN P) WITH MANUAL TRANSMISSION

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

WARRANTY INFORMATION

Dealers should submit a warranty claim on each vehicle completed under this campaign.

Labor Operation *Time Trouble Number Description Allowance Code ------------------------------------------------------------------------- V9336 Inspect for Updated Components .2 hrs 96 V9337 Base Repair Incl. Diagnostics, Air Filter Check/Replace, Glow Plug Check, Fuel Pressure, Hot Startime, Fuel Injection Timing. and Install Kit C/K/G L49 (w/out Turbo) 4.1 hrs 96 C/K L65/L56 (with Turbo) 4.6 hrs 96 V9338 Prom Replace C/K/G .3 hrs 96 V9339 Injection Pump Replace C/K without A/C 3.0 hrs 96 C/K with A/C 3.1 hrs 96 G without A/C 3.6 hrs 96 G with A/C 3.8 hrs 96 T2413 Lube/Oil/Filter C/K/G .5 hr** 96 T2414 EXTRA LABOR TIME Extra labor time is for situations ST** 96 involving extra diagnostic and/or repair time. Extra labor may be used if dealer provides extended service hours to accommodate the customer. Examples would be late right and Saturday hours normally not scheduled. T2412 ALTERNATE TRANSPORTATION Enter cost as "Net Item", coded "M"

* For dealer to receive Administrative Time Allowance associated with this campaign, add 0.1 hour to the Labor Operation Time Allowance.

** Submit actual cost for oil and filter plus 40% mark-up. Enter as Net Item Code "M".

*** Straight Time not to exceed 1/2 of total repair time.

CAMPAIGN IDENTIFICATION LABEL

Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label." Each label provides a space to include the campaign number and five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or ball point pen.

Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in for periodic servicing by the owner.

Apply "Campaign Identification Label" only on a clean, dry surface.

ADMINISTRATIVE PROCEDURE

Procedures covering this campaign are outlined in Section V of your dealership's "GMC Truck Warranty Claims Processing Manual" #P9119 Rev. 2/94.

Dear GMC Truck Owner:

Your complete satisfaction with your 1994 GMC Truck, equipped with a 6.5L Electronic Fuel Injection (EFI) Diesel Engine, is most important to GMC Truck. 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 is equipped with an electronic fuel injection pump which is controlled by a powertrain control module (or computer). CERTAIN Trucks 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 equipped with manual transmissions may exhibit poor acceleration from start characteristics or may stall during deceleration. To address these concerns, your GMC truck 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 GMC Truck 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 an may require between 1 to 6 hours to install, depending on the repairs required.

We've 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.

The enclosed postage paid owner reply card identifies your vehicle. Presentation of this card to your. dealer will assist in making the necessary correction to your vehicle in the shortest possible time. If you have sold or traded your vehicle, please furnish us the complete name and address of the person you sold or traded your vehicle to and return the card to us.

We sincerely regret the inconvenience or concern this situation may cause you. Your satisfaction with GMC products is of utmost concern to us. We have taken this action to ensure your GMC Truck provides years of pleasurable driving experience.

GMC TRUCK DIVISION GENERAL MOTORS CORPORATION

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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.