Envoy 2WD V8-5.3L VIN P (2004)
Body Control Module: Description and Operation
Theft Deterrent - Immobilizer - Some Export Vehicles
CONTENT THEFT DETERRENT (CTD)
Body Control Module (BCM)
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 This is followed by a three minute time-out with the horn no longer active.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.
VEHICLE THEFT DETERRENT (VTD)
Body Control Module (BCM)
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.
