Engine Control Module: Service and Repair
PCM Mounting:
PCM / PROM Access Cover:
PROM Unit Socket:
PCM OR PROM REPLACEMENT
Service of the PCM should normally consist of either replacement of the PCM or a PROM change.
If the diagnostic procedures call for the PCM to be replaced, the engine "calibrator" (PROM) and PCM should be checked first to see if they are the correct parts.
If they are, remove the PROM from the faulty PCM and install it in the new service PCM.
THE SERVICE PCM WILL NOT CONTAIN A PROM. DTC P1623 indicates the PROM is installed improperly or has malfunctioned. When DTC P1623 is observed, check the PROM installation for bent pins or pins not fully seated in the socket. If it is installed correctly and DTC P1623 still appears, replace the PROM.
CAUTION:
- To prevent possible Electrostatic Discharge damage to the PCM or PROM, Do Not touch the component leads, and Do Not remove integrated circuit from carrier.
- When replacing the production PCM with a service PCM (controller), it is important to transfer the broadcast DTC and production PCM number to the service PCM label. Please do not record on PCM cover. This will allow positive identification of PCM parts throughout the service life of the vehicle.
- To prevent internal PCM damage, the ignition must be "OFF" when disconnecting or reconnecting power to PCM (for example, battery cable, PCM pigtail, PCM fuse, jumper cables, etc.).
REMOVE OR DISCONNECT
1. Ignition "OFF," disconnect negative battery cable.
2. PCM splash shield.
3. Connectors from PCM.
4. PCM mounting hardware.
5. PCM from engine compartment.
6. PCM access cover.
7. PROM removal.
CAUTION:
- Replacement PCM is supplied without a PROM, so care should be used when removing it from the defective PCM because it will be reused in the new PCM.
- Using two fingers, push both retaining clips back away from the PROM. At the same time, grasp it at both ends and lift it up out of the socket. Do not remove the cover of the PROM. Use of unapproved PROM removal methods may cause damage to the PROM or socket.
Inspect
Note position of PROM for proper installation in new PCM.
8. New PCM from its packaging and check the service number to make sure it is the same as the defective PCM.
9. Access cover.
INSTALL OR CONNECT
1. PROM in PROM socket.
A. Align small notches in PROM socket.
B. Gently press down on the ends of the PROM until the clips are against the sides of the PROM.
CAUTION: Do Not press on the ends of the PROM until the clips snap into place. Doing so may damage the PCM and/or PROM.
C. Press inward on clips until they snap into place.
2. Access cover on PCM.
3. PCM in engine compartment.
4. Connectors to PCM.
5. PCM splash panel.
6. Negative battery cable.
FUNCTIONAL CHECK
1. Start engine and run for one minute.
2. Scan for DTCs using the Tech 1. If DTC P0325, P1361, P1350 or P1623 occurs, or if the MIL (Service Engine Soon) is "ON" constantly with no diagnostic trouble codes, the PROM is not fully seated or is defective.
- If not fully seated, press inward on clips on sides of PROM until they snap into place.
- If it is necessary to remove the PROM, follow the previous removal instructions.