CAMPAIGN:CRANKSHAFT POSITION SENSOR. Chevrolet Blazer

SUBJECT: INCORRECT CRANKSHAFT POSITION SENSING

MODELS: 1995 Chevrolet/GMC S/T Trucks with 4.3 L Engines (RPO L35)

TO: ALL GENERAL MOTORS DEALERS

General Motors of Canada Limited has determined that certain 1995 S/T trucks equipped with 4.3 L engines (RPO L35 - VIN Code "W") were shipped with a crankshaft position sensing system that may not operate properly. Improper operation of the sensing system could result in ignition misfires and/or cause a Diagostic Trouble Code (DTC) P0337 to be recorded by the Vehicle Control Module.

To correct this condition, it will be necessary to inspect the crankshaft position sensor assembly and the front timing cover, and replace sensor and/or threaded brass insert in the front timing cover, as needed.

VEHICLES INVOLVED:

Involved are certain 1995 S/T trucks equipped with 4.3 L engines (RPO L35) built within the following VIN breakpoint:

Year Model Plant Plant Code From Through

1995 S/T Linden K SK105675 (Chev) SK111599 (Chev) SK501495 (GMC) SK502832 (GMC) 1995 S/T Moraine 2 S2101737 (Chev) S2103129 (Chev) S2500556 (GMC) S2501204 (GMC)

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 information 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.

OWNER 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.

PARTS INFORMATION:

100% of parts required for this campaign will be preshipped to involved dealers of record. This preshipment will occur the week of August 8, 1994. Parts received for recently transferred vehicles should be forwarded by the original dealer (with an accompanying phone call) to the dealer that received the transferred vehicle.

Part Number Description Quantity/Vehicle ----------- ----------- ---------------- 10456256 Sensor Assembly - Crankshaft Position 1

10213295 Insert - Bolt/Screw 1

12525679 Adhesive Sealant 1

12525680 Primer 1

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 ----------- ------------ ------------- 1A Inspect Only (2 WD) .3 2A Inspect Only (4 WD) .4 3A Inspect, Replace Sensor Only (2 WD) .6 4A Inspect, Replace Sensor Only (4 WD) .7 5A Inspect, Replace Sensor and Insert (2 WD) .9 9A Inspect, Replace Sensor and Insert (4 WD) 1.0 T2400 Fuel Top-Off T2401 Wash Vehicle

The amount to be entered in the "Net Amount" column should represent the cost of the fuel required to fill the vehicle's tank for a customer. Note that the amount submitted should represent the self-service price of regular unleaded fuel.

The amount to be entered in the "Net Amount" column should represent the cost for a customer car wash up to $10.00.

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

1. Feed a #10 or #12 gauge wire parallel to the existing crankshaft position sensor wiring. The wire should extend above the serpentine belt tensioner and below the existing crankshaft position sensor in the front cover.

2. Raise the vehicle.

3. Remove the steering linkage shield (4 Wheel Drive only).

4. Verify the crankshaft position sensor part number. The part number is located on the bracket holding the sensor in place. If the stamped part number ends in 254, replacement is necessary.

NOTICE: All vehicles may not require a crankshaft sensor replacement.

5. If the crankshaft position sensor does not need to be replaced, no further action is required. Replace the steering linkage shield, torquing the bolts to 32 Nm (4 Wheel Drive only)

Lower the vehicle. Remove the wire (installed in step #1). The inspection is complete. Proceed to steps 28 and 29.

6. If the crankshaft position sensor replacement is necessary: Continue with procedure.

7. On the engine front cover, open the lower plastic retaining clip and remove the lower section of crankshaft position sensor harness.

8. Remove the crankshaft position sensor retaining bolt and sensor from the engine front cover .

9. Cut the crankshaft position sensor wires at the crankshaft sensor.

10. On the replacement crankshaft position sensor (P/N 10456256):

- Carefully remove the locking collar on the connector.

- Using a suitable pin removal tool, depress the locking tab inside each pin.

- Carefully remove the three (3) wires/pins from the connector and tape the pins together.

- Remove the existing plastic harness clips (2) from the harness.

11. Tape the wire/pins from the new sensor to the #10 or #12 gauge wire (installed in step #1).

12. Lower the vehicle from the hoist. Remove the old crankshaft position sensor wiring harness by pulling up from the engine compartment. Removing the harness will pull a plastic 'rosebud' fastener from the front cover bracket.

13. Carefully pull up on the #10 or 12 gauge feed wire (with new wire harness/sensor attached) to position the new harness between the front cover and water pump.

14. Carefully remove the wire harness from the feed wire. Remove the tape from the connector pins. Push out the locking tab on each connector pin, and re-install each pin in the connector with the following orientation:

Connector position 'A' - White Wire

Connector position 'B' - Black Wire

Connector position 'C' - Red Wire

NOTICE: PINS MUST BE FULLY INSERTED IN THE CONNECTOR AND LOCKED IN PLACE TO ENSURE PROPER OPERATION.

Re-install the locking collar on the connector.

NOTICE: FAILURE TO INSTALL THE WIRES IN THE CORRECT POSITION WILL RESULT IN A NO-START CONDITION, OR SENSOR FAILURE AFTER ENGINE IS STARTED.

15. The sensor harness MUST be routed under the rear A/C compressor bracket. Connect the sensor harness to the engine wiring harness.

16. Raise the vehicle.

17. Check the threaded brass insert in the front cover which holds the crank position sensor/bracket. Run a straight edge across the face of the insert boss. The brass insert should NOT protrude above the front cover boss.

Also check for a loose brass insert. Insert the crankshaft sensor retaining bolt through a washer and fasten to the front cover. Torque the bolt to 7 N.m. If unable to obtain 7 N.m torque, the brass insert is loose and will need to be replaced. Remove the crankshaft sensor retaining bolt. (Go to step 18).

18a. IF NO BRASS INSERT PROTRUSION OR LOOSENESS IS DETECTED, insert the new sensor into front cover.

NOTICE: The sensor MUST BE FULLY SEATED in the front cover hole before installing the retaining bolt. If the sensor is not fully seated, the insert may be pulled out during the torquing procedure. This will result in an increased air gap between the sensor and crankshaft reluctor wheel. An incorrect air gap may result in ignition misfire and/or the illumination of the "Service Engine Soon" light.

Install the crankshaft sensor retaining bolt and torque to 7-9 N.m USING HAND TOOLS ONLY. DO NOT EXCEED THE TORQUE SPECIFICATION.

Re-install the steering linkage shield, if applicable, torquing the bolts to 32 N.m. Lower the vehicle, start and run the engine one (1) minute to verify proper crankshaft position sensor operation.

The repair is now complete. Proceed to steps 28 and 29.

18b. IF THE BRASS INSERT IS LOOSE OR PROTRUDED, the brass insert must be replaced.

Using the crankshaft sensor retaining bolt and a thick stack of washers (approx. 1/2 inch total height) with an I.D. larger than the O.D. of the insert, install the washer(s) between the bolt and insert. The washers must be CENTERED over the insert.

Slowly torque down the crankshaft sensor retaining bolt until the brass insert is pulled out of the front cover, through the center of the washer(s).

19. Clean the insert hole and surface area around it with clean shop air and a clean cloth.

20. Spray the inside of the insert hole with primer (P/N 12525680). IMPORTANT: Let the primer dry for five (5) minutes.

21. Using a saturated cotton swab, apply a generous layer of adhesive (P/N 12525679) to the outside of the new brass insert (P/N 10213295).

22. Using a small hammer, carefully tap the new brass insert into the front cover hole making sure the slotted end is inserted in the hole first. The brass insert must be flush, or slightly lower than the front cover surface.

23. Install the crankshaft position sensor. Check to see that the sensor is fully seated in the front cover hole prior to torquing down the retaining bolt. If the sensor is not fully seated, the insert may be pulled out during the torquing procedure. This will result in an increased air gap between the sensor and crankshaft reluctor wheel. An incorrect air gap may result, in ignition misfire and/or the illumination of the "Service Engine Soon" light.

24. Torque the crankshaft sensor retaining bolt to 7-9 N.m. USING HAND TOOLS ONLY, DO NOT EXCEED THE TORQUE SPECIFICATION.

25. Install the new harness in the lower front cover clip. Check for sufficient clearance between the wiring harness and the harmonic balancer.

26. Aim and hold a heat gun at the newly installed crankshaft sensor retaining bolt head for five (5) minutes to cure the adhesive. Temperature should be approximately 250 degrees Fahrenheit.

NOTICE: THIS STEP IS MANDATORY TO ENSURE PROPER CURING OF RETAINING COMPOUND.

27. Re-install steering linkage shield, if applicable, torquing the bolts to 32 N.m.

28. Lower the vehicle, start and run the engine one (1) minute to verify crankshaft position sensor operation.

29. Install Campaign Identification Label.

30. Wash vehicle and fill fuel tank before returning unit to owner.

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:

General Motors of Canada Limited has determined that certain 1995 Chevrolet/GMC S/T trucks equipped with 4.3 L V6 engines may experience a condition in which the engine crankshaft position sensing system improperly functions. This condition could lead to ignition misfires and the illumination of vehicle's "Service Engine Soon" light.

This service will be provided for you at no charge.

Please contact your GM dealer as soon as possible to arrange a service date.

If parts are required, ask your dealer for details regarding their availability. If parts are not in stock, they can be ordered before scheduling your service date.

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 are sorry to cause you this inconvenience; however, we have taken this action in the interest of your continued satisfaction with our products.

Customer Support Department General Motors of Canada Limited

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.