Engine Control Module: Service and Repair

ECM Mounting:

***UPDATED BY TSB NO. 9002001, JANUARY 11, 1990

CAUTION: To prevent possible electrostatic discharge damage to the ECM, PROM or CALPAK, 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.

NOTE: When replacing the production ECM, it is important to transfer the Broadcast code and production ECM number to the service ECM label. Do not record this information on the ECM cover. This will permit positive identification of ECM parts throughout the service life of the vehicle.

REPLACE ECM

1. Disconnect battery negative cable.
2. Remove center console inside vehicle.
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 Access Cover:

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

PROM Removal Tool:

Using the rocker-type PROM removal tool, engage one end of the PROM carrier with the hook end of the tool. Press on the vertical bar end of the tool and rock the engaged end of the PROM carrier up as far as possible. Engage the opposite end of the PROM carrier in the same manner and rock this end up as far as possible. Repeat this process until PROM and carrier are free from the socket. Use of other than the tool specifically made for this task may damage the PROM or its socket.

Correct PROM Installation:

3. Install new PROM in socket after ensuring that it bears the correct part number for the application. Do not remove PROM from carrier to check number.
4. The small notch in the carrier should be aligned with the small notch in the socket. Press on PROM carrier only until PROM is firmly seated in the socket.
5. Reinstall access cover on ECM and reinstall ECM in vehicle.

REPLACE CALPAK

CALPAK Replacement:

1. Remove ECM and take off access cover.
2. Remove CALPAK with removal tool. Grasp CALPAK carrier from narrow end only and gently rock from end to end while applying an upward force.
3. If a service CALPAK is being installed, ensure that it has the same part number as the original component.
4. Press only on the carrier when installing the CALPAK. The small notch on the carrier must be aligned with the notch in the socket.
5. Reinstall access cover, replace ECM assembly in vehicle and perform a "Diagnostic Circuit Check" to confirm proper installation.