Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Body Control Module
The body control module (BCM) supplies vehicle occupants with visual and audible information and controls various vehicle functions. To provide and receive information, the module is interfaced to the vehicle's serial bus communications network (the Programmable Communication Interface or PCI bus). This network consists of the powertrain control module (PCM), the memory heat seat/mirror module (MHSMM), sentry key immobilizer module (SKIM), the electro/mechanical instrument cluster (MIC), the optional overhead travel information system (OTIS), airbag control module (ORC), optional antilock brakes (ABS), the radio and remote CD player, optional left and right side impact airbag control modules (SIACM), and the optional automatic temperature control (ATC) head. The (BCM) is operational when battery power is supplied to the module, ignition switch power is needed for ignition switched functions. The body control module provides the following features:
Automatic headlamp and fog lamp
A/C switch status/evaporator temperature status
BCM diagnostic support
Central lock and unlock (VTSS only)
Chime
Climate Control (Automatic and Manual) system support
Door ajar switch status
Door Lock Inhibit (key in ignition or headlamps/park lamps on)
Electronic Odometer Support
Fog Lamp Control
Headlamp multiplexing control
Headlamp, Park & tail lamps with battery save feature
Headlamp Time Delay
Illuminated Entry with "fade to off"
Interior lighting with battery save feature
Mechanical Instrument Cluster (fuel level, dim data, odometer & warning chime) support
Memory system (LHS and 300M)
Overhead travel information system
Power door lock multiplexing control
Rear Window Defogger Control
Remote Keyless Entry with Panic Mode
Remote power deck lid release
Remote radio control
Rolling door lock control (customer programmable)
Sentry key immobilizer
Speed proportional steering
Vehicle Theft Security System
Wiper Control (speed sensitive with return to park)
The BCM receives information over the PCI Bus from the PCM in order to support certain features. The required information is as follows:
- Engine RPM
- Engine Temperature
- Injector on Time and Distance Pulses
- Vehicle Speed
- Charging System Failure, Engine Temperature Limp-In, VTSS Arming Status
- Engine Model
- "Check Engine" lamp status
The BCM provides the PCM with information on the A/C switch status and the VTSS status.
The LH has several customer programmable features which can be disabled or enabled by the customer.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.