GM Service Manual Online
For 1990-2009 cars only

Body Control Module (BCM)

The Body Control Module (BCM) is located left of the steering column in the instrument panel and is the theft deterrent system controller. The (BCM) reads the ignition lock cylinder data from the ignition lock cylinder within a certain timing window. If the ignition lock cylinder date is correct, the BCM will communicate a coded password to the Powertrain Control Module™ (PCM) via the class 2 serial data bus. There are two possible causes for the (BCM) to enter a theft mode:


Object Number: 182810  Size: SH
    • An improper ignition lock cylinder timing cycle.
    • Faulty PASSLOCK™ ignition lock cylinder.

Powertrain Control Module (PCM)

The Powertrain Control Module™ (PCM) is located inside of the aircleaner and communicates with the Body Control Module (BCM) via the class 2 serial data bus. Upon receipt of the correct password from the (BCM), the (PCM) enables the fuel injector drivers and the theft deterrent relay, allowing the engine to start and run.


Object Number: 183484  Size: SH

Theft Deterrent Relay

The theft deterrent relay is controlled by the Powertrain Control Module™ (PCM) and is located in the underhood electrical center, in position number 11 labeled CRANK. This relay opens or closes the circuit to start the motor S terminal depending on the command sent by the (PCM).


Object Number: 183488  Size: SH