Engine Control Module: Service and Repair

Service of the PCM should normally consist of either replacement of the PCM or a MEM-CAL change. If the diagnostic procedures call for the PCM to be replaced, the Memory-Calibration unit (MEM-CAL) and PCM should be checked first to see if they are the correct parts.

PCM Location:

When replacing a production PCM with a service PCM, transfer the broadcast code and production number from the production unit to the service unit. Also, replacement PCM does not come from the factory with a MEM-CAL installed in it. During replacement, the MEM-CAL (PROM) must be removed from the PCM being replaced and transferred to the new unit.

NOTE: Before beginning replacement, make sure the ignition switch is turned "OFF".

REMOVE OR DISCONNECT:

1. Negative battery cable.
2. Right hand hush panel.
3. Connectors from the PCM.
4. PCM mounting hardware.
5. PCM from the passenger compartment.
6. PCM "MEM-CAL" access cover.
7. MEM-CAL removal:
NOTE: The replacement PCM is not supplied with a MEM-CAL, so care should be used when removing it from the PCM, because it will be used in the new PCM.

^ Using two fingers, push both retaining clips back away from the MEM-CAL. At the same time, grasp it at both ends and lift it up out of the socket. DO NOT remove the cover of the MEM-CAL.
^ Note the position of the MEM-CAL for proper installation in the new PCM.
8. New PCM from its packaging and check the service number to make sure it is the same as the defective one.
9. access cover.


INSTALL OR CONNECT:

NOTE: When installing a MEM-CAL, the small notches must be aligned with the notches in the socket. Press only on its ends. DO NOT PRESS ON THE CENTER OF THE MEM-CAL UNIT! DAMAGE WILL RESULT. Apply firm even pressure at both ends until the retaining clips snap into place.

1. MEM-CAL in the MEM-CAL socket.
2. Access cover on the PCM.
3. PCM in the passenger compartment.
4. Connectors to the PCM.
5. Right hand hush panel.
6. Negative battery cable.

FUNCTIONAL CHECK:

1. Turn the ignition ON.
2. Enter diagnostics.
a. Allow Code 12 to flash four times to verify no other codes are present. This indicates the MEM-CAL is installed properly and the PCM is functioning.
b. If trouble Codes 42, 43, or 51 occur, or if the "Service Engine Soon" light is ON constantly with no codes, the MEM-CAL is not fully seated or is defective.
^ If not fully seated, press firmly on the ends of the MEM-CAL.
^ If it is necessary to remove the MEM-CAL, follow the previous removal instructions.