Accessing and Reading Diagnostic Trouble Codes

ALDL Connector:

The provision for reading trouble codes is a 3 cavity ALDL connector located behind a kick panel on the passenger side of the vehicle. The ECM has a voltage line to the ALDL connector (Terminal 1). Using a jumper wire, this line is connected to ground (Terminal 3). The ECM will then toggle the "CHECK ENGINE" light to emit any trouble codes stored in the ECM. The output of Code 12 indicates that the "CHECK ENGINE" light is operating normally and will flash if no codes exist. If trouble code(s) exist the lowest numbered code will flash first after Code 12 has been flashed. Each code will flash 3 times. If no codes exist and a driveability problem is present, refer to Diagnosis By Symptom. Testing and Inspection If codes are stored, refer to Diagnostic Charts. Testing and Inspection

To clear the codes from the memory of the ECM, either to determine if the malfunction will occur again or because repair has been completed, the ECM power feed must be disconnected for at least thirty (30) seconds. To remove power from the ECM, remove the 30A main fuse, from relay/fuse center under hood. The negative battery terminal may be disconnected, but this will erase memory in the clock and/or radio.

CAUTION: To prevent ECM damage, the key must be "OFF" when disconnecting or reconnecting ECM power.