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Home >> Chevy Truck >> 1994 >> Lumina APV V6-191 3.1L >> Repair and Diagnosis >> Relays and Modules >> Relays and Modules - Powertrain Management >> Relays and Modules - Computers and Control Systems >> Engine Control Module >> Service and Repair >> Powertrain Control Module (PCM) Replacement

Powertrain Control Module (PCM) Replacement

PROM Access Cover:






CAUTION: To prevent possible Electrostatic Discharge damage to the Powertrain Control Module (PCM), Do Not touch the connector pins or soldered components on the circuit.

Service of the PCM should normally consist of either replacement of the PCM or a Programmable Read Only Memory (PROM) change.

If the diagnostic procedures call for the PCM to be replaced, the engine calibrator (PROM) and PCM should be checked first to see if they are the correct parts. If they are remove the PROM from the faulty PCM and install it in the new service PCM. THE SERVICE PCM 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 the PROM is installed correctly and DTC 51 still shows, replace the PROM.

Important: When replacing the production PCM with a service PCM (controller), it is important to transfer the Broadcast code and production PCM number to the service PCM label. Please do not record on PCM cover. This will allow positive identification of PCM parts throughout the service life of the vehicle.

CAUTION: To prevent internal PCM damage, the ignition must be "OFF" when disconnecting or reconnecting power to PCM (for example, battery cable, PCM pigtail, PCM fuse, jumper cables, etc.).

REMOVE OR DISCONNECT
1. Negative battery cable.
2. Right side sound insulator.
3. Vacuum center.
4. Connectors to PCM.
5. PCM.
6. PROM access cover.
7. PROM from PCM.

INSTALL OR CONNECT
1. PROM to PCM.
2. PROM access cover.
3. PCM.
4. Connectors to PCM.
5. Vacuum center.
6. Right side sound insulator.
7. Negative battery cable.

PROM

CAUTION: To prevent possible Electrostatic Discharge damage to the PROM or PCM, Do Not touch the component leads, and Do Not remove integrated circuit from carrier.

DTC 51 indicates a faulty PROM, bent pins, or incorrect installation.

Important: It is possible to install a PROM backward. If the PROM is installed backward and the ignition key turned to "ON," the PROM circuitry will be destroyed, requiring PROM replacement. The ignition should always be "OFF" when installing or removing the PCM connectors.

REMOVE OR DISCONNECT
1. Negative battery.
2. Right side sound insulator.
3. Vacuum center.
4. Connectors to PCM.
5. PCM.
6. PROM access cover.
7. PROM from PCM.

PROM Removal Tool:






CAUTION: Use 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 the PROM carrier and PROM are free of the PROM socket. The PROM carrier with PROM in it should lift off of the PROM socket easily. PROM carrier should only be removed by using the pictured PROM removal tool. Other methods could cause damage to the PROM or PROM socket.

INSTALL OR CONNECT
1. New PROM carrier in PROM socket.

Inspect New PROM for same part number as old.

NOTE: Do NOT remove PROM from carrier to check PROM number.

PROM In PROM Carrier:





Check reference of PROM in carrier.

NOTE: Small notch of carrier should be aligned with small notch in socket. Press on PROM carrier until it is firmly seated in the socket. Do not press on PROM; only the carrier.

2. Access cover on PCM.
3. PCM.
4. Connectors to PCM.
5. Vacuum center.
6. Right side sound insulator.
7. Negative battery cable.

FUNCTIONAL CHECK
1. Turn ignition "ON."
2. Enter diagnostics (refer to Diagnostic System Check for procedure).
A. Allow DTC 12 to flash four times to verify no other DTC(s) present. This indicates the PROM is installed properly.
B. If Diagnostic Trouble Code (DTC) 51 occurs or if the MIL (Service Engine Soon) is "ON" constantly with no DTC(s), the PROM is not fully seated, installed backwards, has bent pins, or is defective.
^ If not fully seated, press firmly on PROM carrier.
^ If it is necessary to remove the PROM, follow instructions for removal and installation.
^ If installed backwards, REPLACE THE PROM.
^ If pins bend, remove PROM, straighten pins, and reinstall. If bent pins break or crack during straightening, discard PROM and replace it.


CAUTION: Any time the PROM is installed backward and the ignition switch turned "ON," the PROM is destroyed.
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