Engine Control Module: Testing and Inspection

NOTICE: Due to software changes and the removal of the diagnostic enable circuit, Diagnostic Trouble Codes (DTCs) can no longer be obtained by grounding "A" to "B" at the Data Link Connector (DLC). The use of a Tech 1 scan tool will be needed to obtain both current and history DTCs. The Vehicle identification Number (VIN) is programmed into the Powertrain Control Module (PCM) from the factory; therefore, you may not use a PCM from another vehicle for test or replacement purposes. When replacing the PCM the VIN must also be programmed into the new PCM.

To read the DTC(s), use a Tech 1 Scan Tool (or equivalent). To clear the DTCs from memory use the Tech 1 or:

^ ignition "OFF."

^ Disconnect the Fuel / ECM fuse located at the right side underhood electrical center for 30 seconds.

Since the PCM can have a failure which may affect only one circuit, following the diagnostic procedures in this section will determine which circuit has a problem and where it is.

If a diagnostic chart indicates that the PCM connections or PCM is the cause of a problem and the PCM is replaced the Knock Sensor (KS) module must be transferred to the new PCM and the new PCM must then be programmed. If this 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.

^ 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 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."

A shorted solenoid, relay coil, or PCM harness will not damage the PCM but will cause the component to be inoperative.

J 34636 or BT-8405 testers or equivalent provide a fast accurate means of checking for a shorted coil or a short to battery voltage.