Engine Control Module: Service and Repair

ECM Replacement:

When replacing a production ECM with a service ECM, transfer the broadcast code and production number from the production unit to the service unit. The MEMCAL/PROM must be removed from the ECM being replaced and transferred to the new unit.

REMOVE
1. Disconnect battery ground cable.
2. Right hand kick panel.
3. Disconnect computer electrical connectors.
4. Remove computer mounting hardware.
5. Remove computer from passenger compartment.

INSTALL
1. Reverse procedure to install.
2. Perform FUNCTIONAL CHECK

ALDL Connector (Located Underdash):

FUNCTIONAL CHECK
1. Turn ignition "ON."
2. Enter DIAGNOSTIC MODE by jumpering terminals "A" to "B" with key "ON" engine "OFF." A code 12 should flash four times if no other codes are present. This indicates the MEM-CAL/PROM is installed correctly and the ECM is functioning.
3. If codes 19, 42, 43 or 51 occur, or if the "SERVICE ENGINE SOON" light is on consistently with no codes, the MEM-CAL/PROM is not seated properly or is defective. If not fully seated, press firmly on the ends of the MEM-CAL/PROM.
4. Before starting engine reset Idle Air Control valve pintle position:
A. Turn ignition switch to the "ON" position.
B. Ground diagnostic "test" terminal for five seconds.
C. Remove ground.
D. Turn ignition "OFF" for ten seconds.
E. Start engine and check for proper idle operation.

NOTE: Disconnecting ECM from it's power source will clear all ECM memories. Since some operations (particularly IAC valve idle control) are "learned," it may be necessary to partially depress the accelerator pedal when restarting the engine after ECM memory is cleared. It may also be necessary to release the accelerator pedal very slowly when returning to idle, to prevent a stall. This will allow the ECM to "relearn" IAC valve position.

5. Learned operations may be restored by normal driving.