INTERMITTENT ENGINE STALL BUILT AT PONTIAC WEST ASSEMBLY

Subject: INTERMITTENT ENGINE STALL

Model and Year: 1991 S/T TRUCKS BUILT AT PONTIAC WEST ASSEMBLY

TO: ALL CHEVROLET DEALERS

CONDITION:

---------- Some 1991 S/T Trucks built recently at Pontiac West Assembly may be subject to an intermittent engine stall, or a condition where the engine will crank but fails to start. Suspect vehicles were built within the following VIN'S:

M0143685 thru M0145343

CAUSE:

------ This condition is caused by a connector pin that was not manufactured to specification and results in a intermittent loss of contact due to a loose connection at Terminal A-6 (pink wire with black stripe) of the 24 pin ECM connector.

CORRECTION:

----------- For vehicles within the VIN range given above which experience an intermittent engine stall, or fail to start during engine crank, the following procedure should be performed to correct the condition.

1 . Remove the 24 pin connector from the ECM (does not require ECM removal).

2. Remove the blue terminal lock from the "A" row side of the connector.

3. Using instructions on Page 3-93 of the 1990 Fuel & Emissions Book (X-9036), remove terminal A-6, pink wire with black stripe, (Circuit 439) from connector.

4. Using a .95 mm pin gage, check terminal A-6 for correct tension. A good terminal will not allow the pin gage to be inserted without a small amount of force. If the terminal has a loose connection, replace the terminal with P/N 12020757. Do not probe the terminal with anything other than the pin gage, as probing could damage a good terminal.

5. After replacing or checking the terminal, reinstall into the ECM con- -nector and reattach the blue terminal lock. Reinstall the connector into the ECM.

6. Test vehicle by restarting engine and gently moving wiring harness back and forth at 24 pin ECM connector to assure condition has been eliminated.

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.