Engine Control Module: Service and Repair

Electronic Control Module:

CAUTION: To prevent possible electrostatic discharge damage to the ECM or PROM, do not touch connector pins or soldered circuit components. The ignition must always be "OFF" when disconnecting or reconnecting power to the ECM.


Service of the ECM normally consists of either ECM or PROM replacement. If diagnostic procedures call for ECM replacement, check the engine calibrator (PROM) and ECM first to ensure that they are the correct parts. If they are, remove PROM from faulty ECM and install in new service ECM unit. The service ECM will not contain a PROM.


REPLACE ECM

1. Disconnect battery negative cable.
2. Remove right sill plate, door finisher and front kick panel.
3. Disconnect ECM connectors and mounting hardware. Remove ECM.
4. Remove PROM from ECM.
5. Reverse steps to install new ECM.

REPLACE PROM

CAUTION: It is possible to install a PROM backward. PROM circuitry will be immediately destroyed if the unit is incorrectly installed and ignition is turned "ON."

PROM Removal:

1. Remove ECM from vehicle.
2. Remove PROM access cover and remove PROM from ECM as follows:

Using the PROM extraction/insertion tool, start at the opposite end from the reference mark and gently work the tool tang under the PROM with a slight side-to-side rocking motion. Do not attempt to lift the PROM out at this point.

Move tool to the reference end and push extraction tang firmly under PROM with thumb pressing on the tool as close to the tang end as possible. Ensure that tang is completely under the PROM but above the mating socket. Grasp the PROM firmly between thumb and forefinger while pulling upward and remove PROM from socket.

PROM Installation:

3. Ensure that new PROM bears the correct part number for the application.
4. Place PROM on a flat surface with pins down. Press insertion tool firmly down over PROM, making sure reference end can be seen at the tool cut out end.
5. With insertion tool, mate PROM with its socket on ECM circuit board. Ensure that reference ends of both PROM and socket are aligned.
6. Turn the insertion tool over and press PROM down with the blunt end until fully seated. Check for bent pins and proper reference end alignment.
7. Reinstall ECM. If code 51 is displayed or the "Check Engine" light is continuously "ON" with no codes, the PROM may not be fully seated, is installed backward, has bent pins or is defective.