An automotive BCM or body control module is designed to control and monitor various systems much like a typical PCM (power-train control mode). The BCM can be thought as a support computer for everything not power-train related such as the seat controls and memory, seat belt warning, vehicle security systems (including key fob operation), interior lighting, windshield wiper systems, headlight and DRL controls, rear window defroster, dashboard lighting, trunk, lift back, automatic sliding door controls, window controls, cruise control and shift interlock systems. It also shares data within the CAN (controller area network) to additional systems such as the climate control (HVAC), traction control, PCM (powertrain control module), ABS (antilock brake system), SRS (safety restraint system) and the instrument cluster. We use the term BCM but it is also know as a GEM (generic electric module), FCM (Front control module)
As with any computer, any component inside the unit can go bad such as a transistor, IC or resistor. Subject to vibration, heat, coldness and moisture the BCM is built to withstand these conditions to a certain point. Voltage surges and a low battery can also take their toll on the BCM.
If you think the BCM has gone bad you can confirm by perform a
CAN scan which is easier
than it sounds or if you already have a trouble code that indicates such an issue,
this will help any unnecessary repairs. Some manufactures have designed
fuses into their BCM which should
be checked as well.
Locate the BCM in your particular vehicle which will be under the dashboard in
most cases. If you have trouble finding the BCM in your vehicle please
consult one of our technicians.
The BCM is coded to your car which is done in one of two ways, either you can
use a scanner capable of reprogramming which must be done before the unit is removed
or get a used unit which will work in most cases. Also, before removing the unit
disconnect the battery (negative side) and allow the vehicle to sit for more than
15 minutes. Remove the BCM electrical connectors and check for overheating or corrosion
damage which can be repaired without replacement.
Reinstall the new or used unit and reconnect the battery, the BCM will then begin its prompt and relearning procedures.
Our certified technicians are ready to answer BCM questions for free. We hope you saved money and learned from this guide. We are creating a full set of car repair guides. Please subscribe to our 2CarPros YouTube channel and check back often for new videos which are uploaded regularly.