TECH1 ECM CARTRIDGE AND PROC. REVISE TOOL IDLE DRIVE. Chevrolet Corsica 1987

THIS BULLETIN IS A REVISION TO THE TECH 1 DIAGNOSTIC "SCAN" TOOL 1987 THRU 1990 ECM CARTRIDGE.

THE 1987-1990 ECM CARTRIDGE WILL NOT ALLOW THE IDLE LEARN PROCEDURE TO FUNCTION PROPERLY. WHEN PERFORMING AN IDLE RELEARN ON ALL 1987-1991 "A, J, L, W" AND 1990-91 "F" CARLINES EQUIPPED WITH A 2.8L (LB6) OR 3.1L (LH0) SPEED DENSITY (PFI) ENGINE, YOU MUST USE THE 1987-1991 TECH 1 ECM CARTRIDGE OR THE FOLLOWING PROCEDURE.

NOTICE: IF THE ECM IS WITHOUT BATTERY POWER FOR ANY REASON, THE IACV POSITION INFORMATION FOR A STABLE SATSFACTORY ENGINE IDLE IS "LOST" AND IS REPLACED WITH A "DEFAULT" VALUE.

TO RESTORE THE LOST IACV POSITION INFORMATION DUE TO AN ABSENCE OF BATTERY POWER, PERFORM THE FOLLOWING PROCEDURE:

1. RESTORE THE BATTERY POWER AND PLACE AIR CONDITIONING CONTROLS (IF EQUIPPED) IN THE "OFF" POSITION.

2. FIRMLY APPLY THE PARKING BRAKE AND BLOCK THE DRIVE WHEELS. START THE ENGINE, AND SHIFT THE TRANSAXLE TO "DRIVE" FOR AUTOMATICS OR "NEUTRAL" FOR MANUALS.

3. ALLOW THE ENGINE TO RUN A MAXIMUM OF 10 MINUTES OR UNTIL THE ENGINE COOLING FAN HAS CYCLED ONCE, WHICHEVER OCCURS FIRST.

4. SHIFT TRANSAXLE TO PARK (A/T), NEUTRAL (M/T), TURN THE IGNITION KEY TO THE "OFF" POSITION FOR AT LEAST 5 SECONDS.

5. REPEAT STEP #2.

6. ALLOW ENGINE TO RUN FOR AT LEAST 5 MINUTES.

THIS PROCEDURE WILL ALLOW THE ECM MEMORY TO BE UPDATED WITH THE "CORRECT" IACV POSITION AND PROVIDE A STABLE IDLE QUALITY.

DISCLAIMER

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.