Engine Control Module: Testing and Inspection
Programmed VINThe Vehicle Identification Number (VIN) is programmed into the PCM. Do not exchange a PCM from another vehicle for testing or replacement. When replacing the PCM, the VIN must also be programmed into the new PCM.
Circuit Diagnosis
Because the PCM can have a failure which may affect only one circuit, follow the diagnostic procedures to determine which circuit has a problem and where it is.
New PCM, Fault Still Present
If a diagnostic chart indicates that the PCM connections or PCM is the cause of a problem and the PCM is replaced, but does not correct the problem, one of the following may be the reason:
^ There is a problem with the PCM terminal connections. The diagnostic chart will say PCM connections or PCM. The terminals may have to be removed from the connector in order to check them properly.
^ EEPROM program is not correct for the application. Incorrect components may cause a malfunction and may or may not set a Diagnostic Trouble Code (DTC).
^ The problem is intermittent. This means that the problem is not present at the time the system is being checked. In this case, refer to the Symptoms portion of the manual and make a careful physical inspection of all components and wiring associated with the affected system.
^ There is a shorted solenoid, relay coil, or harness. Solenoids and relays are turned ON and OFF by the PCM using internal electronic switches called drivers. Each driver is part of a group of seven called Output Driver Modules. A shorted solenoid, relay coil, or harness will not damage the PCM but will cause the solenoid or relay to be inoperative. The J 34636 tester, or equivalent, provides a fast, accurate means of checking for a shorted coil or a short to battery voltage.