The Diagnostic Tables incorporate diagnosis procedures using a scan tool such as the Tech 1 Diagnostic Computer with the Vehicle Interface Module (VIM) where possible.

The scan tool saves time in diagnosis. The scan tool also prevents the replacement of good parts. In order to use the scan tool successfully for diagnosis, the technician must understand the system being diagnosed as well as understanding the limitations of the tool.

Refer to Vehicle Control Module (VCM) and Vehicle Control Module (Serial Data Communication) for more information.

In order to read the DTCs, use a scan tool. The technician cannot flash the DTCs by grounding the DLC.

Use the scan tool in order to clear the DTCs from the memory.

If a diagnostic table indicates that a VCM connection or the VCM is the cause of a problem and the technician replaces the VCM but the problem is not eliminated, one of the following items may be the reason.

1. After replacing the VCM, the EEPROM was not reprogrammed correctly. Refer to EEPROM Programming .
2. A problem may exist with the VCM terminal connections: In order to check the connections properly, remove the terminals from the connections.

The VCM is not correct for the application: The incorrect components may cause a malfunction and may or may not set a DTC.

3. The problem is an intermittent: Refer to the Driveability Symptoms. Make a careful physical inspection of all portions of the system involved.
4. A shorted solenoid, relay coil or harness may exist: The VCM turns the solenoids and relays ON and OFF by the VCM by using internal electronic switches called drivers. Each driver is a part of a group of 4 called quad-drivers. Failure of 1 driver can damage any other driver in the set.
5. The replacement VCM may be malfunctioning: After replacing the VCM, recheck the system for proper operation. If the diagnostic table again indicates that the VCM is the problem, substitute a known good VCM.

A shorted solenoid, relay coil, or harness will not damage the quad drivers in the VCM. A shorted solenoid, relay coil, or harness will cause the circuit and the controlled component to be inoperative.

When the circuit fault is not present or the technician has repaired the fault, the quad driver will again operate in a normal manner due to its fault protected design.

If the technician has repaired a fault in the a circuit controlled by a quad-driver, reinstall the original VCM. Check the circuit for proper operation.

A VCM replacement is not necessary if the repaired circuit or component operates correctly.

A J 39200 tester provides a fast, accurate means of checking for a shorted coil or a short to battery voltage.

Since this is the starting point for the diagnostic procedures or finding the cause of an emissions test failure, always begin here.

The circuit check is performed through the sixteen terminal Diagnostic Link Connector (DLC) under the instrument panel in the passenger compartment.