Engine Control Module: Service and Repair

Powertrain Control Module (PCM):

Service of the Powertrain Control Module (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.

NOTE: THE SERVICE PCM WILL NOT CONTAIN A PROM. DTC P1623 indicates the PROM is installed improperly or has malfunctioned. When DTC P1623 is encountered, check the PCM installation for bent pins or pins not fully seated in the socket. If it is installed correctly and DTC Pl623 still sets, replace the PROM. 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 code 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.).

PROM Removal:

PCM And PROM:

NOTE: The PROM is "keyed" to prohibit improper insertion. However, it is essential that the correct PROM be used with a specific vehicle model.

CAUTION: The ignition should always be OFF when installing or removing the PCM connectors.

REMOVE OR DISCONNECT
1. Negative battery cable.
2. PCM from mounting hardware.
3. Harness connectors from PCM.
4. PCM from engine compartment.
5. PROM access cover.
6. Remove PROM by using thumb and first finger to gently squeeze each end of the blue PROM carrier and pull upward.

INSTALL OR CONNECT
1. PROM in PCM.

NOTE: Gently press on PROM until it is firmly seated in the socket.

2. PROM access cover.
3. Connectors to PCM.
4. PCM into vehicle.
5. Negative battery cable.


FUNCTIONAL CHECK
1. Perform on-board diagnostic system check.
2. Start engine and run for one minute.
3. Scan for DTCs using the Tech 1.
4. 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 it is necessary to remove the PROM, follow the previous removal instructions.