FBC System Check

Turn diagnostic switch on, located under steering column left side of dash. See Fig 1 . Turn ignition on, but do not start engine. CHECK ENGINE light will begin to flash a code 12.
Code 12 will flash 3 times, then any trouble code stored in ECM memory will flash 3 times and continue to cycle in this sequence. See Fig 2 . A code 12 consists of one flash, a short pause and 2 flashes.
Code 12 is a normal operation and means diagnostic system is functioning properly. After a code 12 flashes, any trouble codes stored in ECM memory will begin to flash. See Fig 4 .

Fig 1: Location of Diagnostic Switch

Courtesy of GENERAL MOTORS CORP.

Fig 2: Diagnostic Flow Chart

Courtesy of GENERAL MOTORS CORP.

Fig 3: Diagnostic Flow Chart

Fig 4: Diagnostic Code Chart

Courtesy of GENERAL MOTORS CORP.