Body Control Module (BCM)
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 Chevrolet Tahoe, 2003 Chevrolet Suburban, and 2003 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
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
- 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.