The body control module (BCM) is capable of controlling multiple body functions. Components directly connected to the BCM are controlled by the BCM's outputs. The BCM controls the outputs based on input information that it obtains from the sensors and the switches that are directly connected to it. The BCM can also borrow information from other vehicle systems connected to the Class 2 serial data link. The BCM evaluates this information and controls certain body systems by commanding an output ON or OFF.

The BCM is also capable of commanding other vehicle systems to control functions that are not directly wired and/or controlled by the BCM. The BCM accomplishes this task by sending specific messages on the Class 2 serial data link. The vehicle system capable of performing such function will respond to the BCM message.

The BCM controls the following functions:

Passlock™ is a vehicle theft deterrent system. This system contains an ignition key sensor called a Passlock™ sensor. The Passlock™ sensor is part of the ignition lock cylinder assembly. The BCM provides power and ground for the Passlock™ sensor.

When turning the ignition switch to the start position with the proper key, the Passlock™ sensor generates an analog voltage signal. This signal is sent through the Passlock™ detecting circuit. This analog voltage signal is of a specific value to the vehicle, and varies from vehicle to vehicle. When attempting to start the engine, the BCM compares a preset stored analog voltage value with the signal coming from the sensor. Because both values match, the BCM sends a fuel enable password via the Class 2 serial data link to the powertrain control module (PCM) or the vehicle control module (VCM), depending on your powertrain option. As a result, the PCM/VCM allows fuel delivery to the engine.

When attempting to start the engine without the proper key in the ignition switch, the Passlock™ sensor sends an analog voltage signal of a different value. The BCM compares the preset stored analog voltage value with the signal coming from the sensor. Because both values do not match, the BCM sends a fuel disable password via the Class 2 serial data link to the PCM/VCM. As a result, the PCM/VCM disables the fuel delivery to the engine and the vehicle will not start.

The BCM has 3 main voltage feeds CKT 1140, CKT 39, and CKT 41 and 2 grounds on CKT 1850.