Engine Control Module: Service and Repair

CAUTION: The Powertrain Control Module (PCM) on this vehicle should not be removed without reviewing service procedures of the PCM and EEPROM. Replacement and/or removal of the PCM may cause the EEPROM memory to reset and the vehicle to have a no start or poor running condition. Replacement of the Instrument Panel Cluster may also cause the EEPROM to reset. CHECK WITH A DEALER BEFORE PERFORMING PCM REPLACEMENT.




When replacing a production Computer with a service Computer, transfer the broadcast code and production number from the production unit to the service unit. Also during replacement, knock sensor module must be removed from the computer being replaced and transferred to the new unit.

NOTE: These units do not have a replaceable PROM. An Electronically Eraseable Programmable Read Only Memory (EEPROM) is built into the PCM. The EEPROM may be a photo-sensitive type (program will be erased if exposed to light). These units must be programmed using General Motors "TECHLINE" terminal equipment. The replacement PCM is supplied without an EEPROM program. If this equipment is not available for your use, DO NOT attempt to replace PCM.

Removing/Replacing Knock Sensor Module:

Knock Sensor Module - Removing From PCM:

PCM Location.:

REMOVE
- Disconnect battery ground cable.
- Right hand kick panel.
- Disconnect computer electrical connectors.
- Remove computer mounting hardware.
- Remove computer from passenger compartment.
- Remove knock sensor module from PCM (see illustration).

INSTALL
- Reverse procedure to install.
- Perform FUNCTIONAL CHECK to verify proper installation.

Data Link Connector (DLC) - Located Underdash:

FUNCTIONAL CHECK:

- Turn the ignition ON.
- Enter diagnostics.
^ Code 12 should flash. This indicates the PCM is functioning.


NOTE
Disconnecting PCM from it's power source will clear all PCM memories. Since some operations (particularly IAC valve idle control) are "learned", it may be necessary to partially depress the accelerator pedal when restarting the engine after PCM memory is cleared. It may also be necessary to release the accelerator pedal very slowly when returning to idle, to prevent a stall. This will allow the PCM to "relearn" IAC valve position. Learned operations may be restored by normal driving.