Body Control Module: Description and Operation

CONTENT THEFT DETERRENT (CTD)

Body Control Module (BCM)
The body control module (BCM) monitors several inputs in order to arm and disarm the CTD system. The BCM controls the alarm function outputs. When the BCM detects an unauthorized entry (any door opened), the BCM applies ground to the horn, the park lamp and the headlamp relays. The BCM will send messages to the security telltale in the instrument cluster through the Class 2 serial data link. The BCM has the following 8 basic modes for operating the CTD system. The more detailed descriptions are below.
- Off state
- Idle state
- Disarmed state
- Ready-to-arm state
- Arm initiated state
- Arm delay state
- Armed state
- Alarm state

The BCM has the following 6 discrete inputs in order to monitor the CTD system:
- Ignition 1
- Driver door latch (door jamb) switch
- Passenger door latch (door jamb) switch
- Door lock relay
- Door key switch
- Passenger door unlock relay

The BCM applies ground once per second for approximately 2 minutes, or until a valid input to disarm the system is received by the BCM.

VEHICLE THEFT DETERRENT (VTD)

Body Control Module (BCM)
The Body Control Module (BCM) contains the theft deterrent system logic. The BCM reads the Passlock(TM) data from the Passlock(TM) sensor. If the Passlock(TM) data is correct, the BCM will pass theft. The BCM will then transmit the fuel continue password to the VCM/PCM.

During the tamper mode the vehicle may start. The vehicle will then stall. If the BCM receives the wrong Passlock(TM) data, the VTD will immediately go into the tamper mode. The tamper mode will lock-out the vehicle fuel injectors for 10 minutes. The SECURITY indicator will flash while the VTD is in the tamper mode.

If the Passlock(TM) sensor sends a correct password to the BCM when the ignition is in the ON position, the BCM will send a fuel enable signal to the VCM/PCM. The VCM/PCM will not disable the fuel due to any BCM message for the remainder of the ignition cycle.