Powertrain Control Module - PCM

Before using this section, you should be familiar with the information and the proper diagnosing procedures. If the proper diagnosis procedures are not followed, it may result in unnecessary replacement of good parts.

If a diagnostic chart indicates that a PCM connection 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 terminals may need to be removed from the connector in order to check them properly.

^ The PCM is not correct for the application - The incorrect components may cause a malfunction and may, or may not set a 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 DIAGNOSIS BY SYMPTOM/INTERMITTENTS - Intermittent Malfunctions. and make a careful physical inspection of all portions of the system involved.

^ 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 four called "quad-drivers." Failure of one driver can damage any other driver in the set.
A shorted solenoid, relay coil, or harness will not damage the "quad-drivers" in this PCM, but will cause the circuit and controlled component to be inoperative. When the circuit fault is not present or has been repaired, the "quad-driver" will again operate in a normal manner due to its fault protected design. If a fault has been repaired in a circuit, controlled by a "quad-driver," the original PCM should be reinstalled and the circuit checked for proper operation. PCM replacement will not be necessary if the repaired circuit or component operates correctly.
The J 39200 tester, or equivalent, provides a fast, accurate means of checking for a shorted coil, or a short to battery voltage.

^ The replacement PCM may be faulty - After the PCM is replaced, the system should be rechecked for proper operation. If the diagnostic chart again indicates that the PCM is the problem, substitute a known good PCM.