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™ Sensor. The BCM also measures the voltage of the security sensor signal circuit. The voltage measured will indicate whether the Passlock™ 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 ECM. 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 ECM, and the vehicle will not start.