WARNING: Deactivate air bag system before performing any service operation. See appropriate AIR BAG RESTRAINT SYSTEMS article. Do not apply electrical power to any component on steering column without first deactivating air bag system. Air bag may deploy.

Body Control Module (BCM) performs the following functions: exterior and interior lighting control, battery rundown protection, chime, instrument cluster indicator control, power door locks, remote keyless entry and theft deterrent.

BCM communicates with components using class 2 data line. Class 2 data line is used by BCM to communicate with the Driver Information Display Module, Driver Seat Adjuster Memory Module, Electronic Brake Control Module (EBCM), inflatable restraint Sensing and Diagnostic Module (SDM), instrument cluster, Powertrain Control Module (PCM), Transfer Case Shift Control Module and Vehicle Interface Unit (VIU). Class 2 serial data uses the peer-to-peer method and message arbitration to manage data line traffic.

Signals that activate the BCM are known as "wake-up" signals. BCM wake-up signals include: door ajar switches, door handle switches, dome light, parking lights, key in ignition, key removed from ignition, key in door lock, when ignition switch is turned to RUN position, or inadvertent power.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Body Control Modules: Description

Use the Manual With the Right Hardware

When to See a Mechanic

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