Retrieving Codes
- Perform DIAGNOSTIC CIRCUIT CHECK before diagnosing vehicle using self-diagnostic system. See DIAGNOSTIC CIRCUIT CHECK chart in this article.
- Ensure ignition switch is in the "OFF" position. Using a jumper wire, ground diagnostic connector terminal to ground terminal. See Fig 1
. Connector is located in the engine compartment. Turn ignition switch to the "ON" position. Read trouble codes.
- If no trouble codes are stored, "CHECK ENGINE" light will flash rapidly on then off until jumper wire is disconnected. Count the number of flashes and look for pauses in flashing to ensure no trouble codes are overlooked. If trouble codes are stored, code will flash 3 times.
Courtesy of GENERAL MOTORS CORP.