I own a Fiat Grande Punto. Recently I was told by the authorized auto workshop that the BCM in my car has failed and needs to be fixed.

So I have two questions regarding this:

  1. What is the BCM and what does it do?
  2. They asked me to give them certain code numbers which came with my car manual and are unique to my car to them. They said they needed it to reprogram the BCM. What is the significance of those code numbers?

4 Answers 4


The Body Control Module is a computer which controls many things in your car not directly related to the engine. Instead of large wiring looms circuits all over the car all the buttons connect to a single computer which in turn turns on the headlights, open the windows, control the central door locking, etc. =A good example is the VAGCOM system in Volkswagens and Audi's.= see comment)

A Body Control Module is almost always specifically programmed to work with a specific car. For example, a BCM of another vehicle will not open the doors when you use your key or remote. Also, when you try to start the engine it checks the number of the key and a number in the Engine Control Unit as a anti-theft mechanism. Your ECU also does this check, but your BCM can do additional checks like locking the doors to prevent the thief from leaving.

  • 1
    VAGCOM (now called VCDS) is just a third party software to configure controllers in VW vehicles; it isn't a "system" and it isn't part of the vehicle.
    – user5106
    Commented Dec 26, 2014 at 18:16
  • Uhh, the BCM can lock you in to your car? That doesn't sound right...
    – Cullub
    Commented Dec 7, 2018 at 18:02
  • @Cullub two ways that can happen. 1, is no physical door lock control. If its only electric, and the bcm refuses to unlock, then you are stuck. 2, and I've had this happen on my old 99 Camry, is if the anti-theft is triggered due to the door lock being open without disarming and NOT from the key turning, like sticking a wire through the door sill/frame, it will immediately try to lock the doors again. This can effectively prevent a door from being open.
    – cde
    Commented Dec 9, 2018 at 2:15

My 2004 Saturn 2004 would not stary on cold mornings. The triple AAA came out and found checked the battery and alternator was just fine.

After being in the shop for quite some time the found it was the body control module. That is the computer brains of the system.


The BCM (Body Control Module) is the electronic control unit that monitors and controls all of the systems in the car body. Electric windows,A/C functions, electric mirrors,electric locks,security systems, etc. It communicates with all the other modules via the cars vehicle bus. It drives all the relays the control all the nice gadgets. As with all the vehicular modules it generates fault codes for problem diagnosis.


bcm= body control module

it is one of many computers in modern cars. It reports back to the main computer with trouble codes. read on a scanner unit most shops should but probably don't have.the bcm involves accessories like windows up and down, and a bunch of other things.

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