With Vehicle Control Module (VCM)

DIAGNOSIS
Diagnostic charts incorporate diagnosis procedures using a scan tool, such as the Tech 1 Diagnostic Computer, where possible. The scan tool has the ability to save time in diagnosis and prevent the replacement of good parts. The key to using the scan tool successfully for diagnosis lies in the technician's ability to understand the system being diagnosed. as well as an understanding of the scan tool's limitations. Refer to Vehicle On-Board Diagnosis for more information. Testing and Inspection

To read Diagnostic Trouble Codes (DTCs), a scan tool must be used. DTCs cannot be flashed by grounding the Data Link Connector (DLC).

To clear the DTCs from memory remove Vehicle Control Module (VCM) power fuse for 30 seconds while ignition is "OFF."

If a diagnostic chart indicates that a VCM connection or VCM is the cause of a problem and the VCM is replaced, but does not correct the problem, one of the following may be the reason.

^ The VCM was replaced and not reprogrammed correctly. Refer to Electrically Erasable Programmable Read Only Memory (EEPROM) programming procedure in "On-Vehicle Service."

^ There is a problem with the VCM terminal connections - The terminals may need to be removed from the connector in order to check them properly.

^ The VCM 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 and make a careful physical inspection of all portions of the system involved. Testing and Inspection

^ Shorted solenoid. relay coil. or harness - Solenoids and relays are turned "ON" and "OFF" by the VCM using internal electronic switches called "drivers." Each driver is part of a group of four called "quad-drivers." Failure of one driver can darnage any other driver in the set.

A shorted solenoid, relay coil, or harness will not damage the "quad-drivers" in the VCM 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 VCM should be reinstalled and the circuit checked for proper operation. VCM replacement will not be necessary if the repaired circuit or component operates correctly.

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