Self-Diagnostic System Check
- Locate ALDL diagnostic connector near ECM. Using a jumper wire, jump between terminals "A" and "C". See Fig 1
. Turn ignition on, but do not start engine. CHECK ENGINE light will begin to flash diagnostic code 12 indicating the system is working.
- Code 12 will flash 3 times, then any additional code will flash 3 times and continue to cycle in this sequence up to a maximum of 3 codes. A code 12 consists of one flash, a short pause and 2 flashes. See Fig 2
.
- To clear codes, remove the 10A ECM fuse in the fuse box for 10 seconds.
Courtesy of GENERAL MOTORS CORP.
Courtesy of GENERAL MOTORS CORP.