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Bad Body Control Module? Here’s How to Tell

You’ve probably never thought about the body control module (BCM) in your car, but this component plays an important and comprehensive role in how the electrical features of your vehicle operate. Since the BCM touches on so many different systems, it’s not always obvious when things start to go awry. Check out this brief explanation of the BCM and the symptoms that could indicate it’s on the fritz.

What the BCM Does

It’s a bit strange to think that something connects your vehicle’s door locks, windows, headlights and windshield wipers, but that’s exactly what the body control module does. It links together various electronic dashboardvehicle features and keeps them under central surveillance to make it easier for your automobile to operate them. While there might not be much of a functional link between your power sunroof and your gauge cluster, having them all under one roof is a common practice in automotive design.

Common Trouble Signs

One of the keys to diagnosing a problem with the body control module versus an issue with an individual component is sudden, unusual behavior. Examples include flashing dash lights, a stereo system switching from AM to CD in the middle of a broadcast, the horn honking when you put down a specific window or hazard lights activating themselves in the middle of a drive.

If one or more of these symptoms are present at the same time, chances are it’s an issue with the BCM, and not the statistically less likely situation of multiple vehicle features failing simultaneously. If the problems occur intermittently, however, you might need to look into other causes, such as a bad battery or alternator – which won’t provide the level of voltage required for normal operation – or an issue with the fuses or relays in the electrical system. You can use a circuit tester to troubleshoot the electrical system yourself, but sensor issues are often best left to your local mechanic.

How to Repair a Body Control Module

Most of the time, a damaged BCM will have to be replaced and can’t be repaired. Water, vibration, heat and age can all contribute to a module failing, which, depending on the placement of the unit in your vehicle, can be difficult to avoid.

To keep your new BCM in the best shape possible, make sure it stays clean and dry, and protect it from unwanted shaking or excessive heat if at all possible.

Check out all the electrical parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on your vehicle’s body control module, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Flickr.

about author

Benjamin Hunting

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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