Body Control Module: Description and Operation

BODY CONTROL MODULE (BCM)

The CTD system is an internal function of the Body Control Module (BCM) which utilizes class 2 serial data and various switch input information to perform CTD functions. When the BCM detects an unauthorized entry, it activates the horns and exterior lamps. The BCM has five basic modes (disarmed, standby, delayed, armed, and alarm) for operating the CTD system. The different modes are described below.
1. The BCM has the CTD system in a disarmed mode until the following conditions are detected:
- Ignition key turned to the OFF position.
- Any door open.
- Doors locked by either the power door lock switch or the LOCK button on the transmitter.
2. The BCM enters the standby mode when the above conditions are detected. In standby mode, the BCM commands the SECURITY indicator to flash. If all the doors are closed and the LOCK button on the transmitter is used, the BCM enters the delayed mode.
3. When the last door is closed, the BCM enters the delayed mode for 30 seconds. In delayed mode the BCM commands the SECURITY indicator to illuminate ON steady.
4. After 30 seconds, the BCM enters the armed mode. Any forced entry activates the alarm mode.
5. When the BCM detects a forced entry, the BCM enters the alarm mode. The BCM activates the horns and exterior lamps for 2 minutes. This is followed by a three minute time-out with the horn no longer active. If no new intrusions are detected after the time-out, the horn is not active.The system must be disarmed or the intrusion condition removed after the time-out for the system to exit alarm mode.

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 send a class 2 message to the PCM to enable the fuel injectors and crank relay. During the tamper mode the vehicle may start. The vehicle will then stall. If the BCM receives the wrong Passlock(tm) data, the VTD system will immediately go into the tamper mode. The tamper mode will lock-out the vehicle fuel injectors and crank relay 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 and crank relay enable signal to the PCM.