Engine Control Module: Service and Repair

ECM Location/Installation:

Engine Control Module (ECM):

SERVICE NOTES
Service of the ECM should, normally, consist of either replacement of the ECM or a PROM change.

If the diagnostic procedures call for the ECM to be replaced, the engine calibrator PROM and ECM should be checked first to see if they are the correct parts. If they are, remove the PROM from the faulty ECM and install it in the new service ECM. THE SERVICE ECM WILL NOT CONTAIN A PROM.
Diagnostic Trouble Code (DTC) 51 indicates the PROM is installed improperly or has malfunctioned. When DTC 51 is obtained, check the PROM installation for bent pins or pins not fully seated in the socket. If it is installed correctly and DTC 51 still shows, replace the PROM.

NOTE: When replacing the production ECM with a service ECM (controller), it is important to transfer the broadcast code and production ECM number to the service ECM label. Please Do Not record on ECM cover. This will allow positive identification of ECM parts throughout the service life of the vehicle.

CAUTION:
- To prevent internal ECM damage, the ignition must be "OFF," when disconnecting or reconnecting power to ECM (for example, battery cable, ECM pigtail, ECM fuse, jumper cables, etc.).
- To prevent possible electrostatic discharge damage to the ECM, Do Not touch the connector pins or soldered components on the circuit board.

REMOVE OR DISCONNECT

1. Negative battery cable.
2. ECM mounting hardware.
3. ECM connector cover.
4. Connectors from ECM.
5. ECM.
6. ECM access cover.
7. PROM removal.

Caution:
- Replacement ECM is supplied without a PROM, so care should be used when removing it from the defective ECM because it will be reused in the new ECM.
- To prevent possible electrostatic discharge damage to the PROM, Do Not touch the component leads, and Do Not remove integrated circuit from carrier.

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 or ECM circuit board.

Inspect
For alignment notches of the PROM and carefully set it aside. Do Not open the PROM.

IF ECM IS BEING REPLACED - REMOVE OR DISCONNECT

1. New ECM from its packaging and check the service number to make sure it is the same as the defective ECM.
2. Access cover.

INSTALL OR CONNECT

1. PROM in PROM socket.

CAUTION: Gently press down on the ends of the PROM until the clips are against the sides of the PROM. DO NOT press on the ends of the PROM until the clips snap into place, because the controller circuit board and/or clips may be damaged. Press inward on the clips until they snap into place.

2. Access cover on ECM.
3. Connectors to ECM.
4. ECM connector cover.
5. ECM mounting hardware.
6. Negative battery cable.

FUNCTIONAL CHECK
1. Turn ignition "ON."
2. Enter diagnostics.
A. Allow DTC 12 to flash four times to verify no other DTCs are present. This indicates the PROM is installed properly and the ECM is functioning.
B. If Diagnostic Trouble Code (DTC) 51 occurs, or if the Malfunction Indicator Lamp (MIL) "Service Engine Soon" is "ON" constantly with no DTCs, the PROM is not fully seated or is defective.

- If it is necessary to remove or reinstall the PROM, follow the previous instructions.