WARNING: This page is about a different car, the 1999 GMC Sierra and 1999 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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) is designed to process various input information it receives from sensors and switches or borrows from other vehicle systems connected to Class 2 serial data link. BCM evaluates this information and controls certain body systems by commanding an output on or off.

BCM can also command other vehicle systems to control functions by sending specific messages over Class 2 serial data link. BCM controls operation of audible warnings, indicator warnings, power door locks, remote keyless entry, Passlock(tm) theft deterrent, content theft deterrent, interior and exterior illumination.

BCM goes into low power mode (asleep state) when ignition has been turned off and 20 minutes have elapsed without any wake-up signals. BCM goes into high power mode (wake-up state) after receiving any wake-up signals.

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

Section 11 (Body Control Modules): Description

Use the Manual With the Right Hardware

When to See a Mechanic

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