Bravada 2WD L6-4.2L VIN S (2002)
Body Control Module: Description and Operation
The CTD system is an internal function of the Body Control Module (BCM) which utilizes class 2 serial data from the Driver Door Module (DDM),
Passenger Door Module (PDM) and the Liftgate Module (LGM) and various switch input information to perform CTD functions.
When the BCM detects an unauthorized entry, it activates the horns and exterior lamps. When the BCM detects an unauthorized 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 This is followed by a three minute time-out with the horn no longer
active.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 BCM contains the logic of the theft deterrent system. The BCM provides the battery positive voltage to operate the Passlock(TM) Sensor. The BCM
also measures the voltage of the security sensor signal circuit. The voltage measured will indicate whether the Passlock(TM) Sensor has been activated
and whether the resistance value from the sensor is a valid value or the tamper value. If voltage measured is in the valid range, the BCM compares this
voltage, voltage code, to a previously learned voltage code. If the voltage codes match, the BCM sends a class 2 message containing a password to the
PCM. If the voltage codes do not match, or the voltage is in the Tamper range, or there is a circuit fault, the BCM will not send the correct password to
the PCM, and the vehicle will not start.