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Modern vehicles have several computerized systems; in most cases, these systems provide feedback to different modules. The modules analyzes the feedback and optimizes the engine’s performance so your car can drive well.
One of the commonest – and very important – modules found in today’s cars is the BCM (Body Control Module). The body control module monitors many electronic accessories in your vehicle. If this module goes bad, those monitored accessories will stop functioning or fluctuate.
Therefore, it’s pretty important that you know the common symptoms of a bad body control module so that when it starts failing, you’d know and act fast to fix the issue(s), and that is what we will discuss in this article.
What Does a Body Control Module Do?
The BCM is an electronic control unit installed in virtually all modern cars. Its function is to monitor and control the car’s body accessories, such as the power windows & mirrors, immobilizer system, air conditioning, central locking, wiper, heater system, anti-theft accessories, and pretty others.
The number of systems or accessories monitored and controlled by the BCM varies by vehicle model. Also, the body control module sends signals to other “control modules” and computerized units (ex., the ECU or PCM) in motor vehicles.
When this module goes bad, it will stop controlling the load drivers and actuating relays that power most accessories in your car.
In most vehicles, the BCM is located beneath the dashboard, which is the same location most other vehicle modules are installed. Of course, the exact location varies by car model and makes, but it’d always be close to beneath the dashboard – the driver’s side – for easy troubleshooting.
What Causes a Body Control Module To Go Bad?
There are quite several reasons why the BCM may go bad, and these reasons are not uncommon. Some of the commonest reasons include:
- Hard impact from collisions
- Faulty or loose wiring
- Faulty sensors
- Engine overheating
- Excessive shuddering/vibrations
Body Control Module Problems | Symptoms of a Bad Body Control Module
When the BCM goes bad, you’d most likely notice these symptoms explained below. However, these symptoms could also show up if some other modules or sensors go bad in a vehicle.
But then, if you experience any of these, have the check inspected for a potentially bad BCM and fix it up pretty early before it causes more damage that could cost much more to fix.
1. Check Engine Icon Lights Up
Yeah, this is a common sign that you need to check on your car’s engine, sensors, or systems; the illumination of the check engine icon can mean a lot of things, and a bad BCM is one of those signs.
Hence, when the icon illuminates, you should check on the BCM, along with other components that could possibly throw up the notification.
2. Parasitic Drain
If you wake up every day to a dead battery – and you’re sure the battery and alternator aren’t weak – it could be that your car’s BCM has gone bad.
The BCM is responsible for sending electric current to quite many accessories in your car, so when it’s bad, it may be sending electric current to those accessories at the wrong time – even when your car is not turned on, and that would cause the car’s battery to run down constantly.
3. Car Won’t Start
Yes, a bad body control module can cause a vehicle not to start at all. There are many ways a bad BCM can cause your car not to start, but mainly by causing parasitic draw – causing the battery to drain much faster when the car is parked or idling.
Also, a faulty BCM may not be able to supply enough current to the ignition system to start the car – this happens in rare cases anyway.
4. Multiple Dashboard Lights Illuminate at Once
If you turn on the car and notice that multiple dashboard lights are illuminated, that could be a sign that your vehicle’s body control module is bad.
Since the module controls and powers many accessories, its failure can trigger multiple lights – connecting to those accessories, the BCM monitors – to come on.
5. Erratic Accessories Performance
Another thing a bad BCM could do is trigger erratic response or performance of the connected systems and accessories. For example, your car’ horn would go off at random intervals without you engaging it, or the lights flicker on and off intermittently.
Also, it could cause the wipers to engage randomly even when it’s not raining, and you didn’t turn or flip the wiper control.
If your car comes with power windows and mirrors, a bad BCM can cause the “power” function to stop working, and your car’s alarm may go off randomly too.
There are just many uncommon scenarios that could occur when you’ve got to deal with a bad body control module. When these start happening, troubleshoot the car to find the exact cause.
6. Remote Access Problems
A bad BCM may prevent your car from starting remotely – using your car’s remote key or app. This happens when the BCM cannot actuate and power the relevant chips that power those remote access utilities and components.
Also, in some cases, a bad BCM would unlock your car after you’ve locked it – or vice versa – using the remote control.
Body Control Module Replacement Cost
In most cases, you don’t really need to replace the module itself – a simple reset could fix everything back up. Notwithstanding, if the module is physically damaged, you’d need to replace it entirely.
The replacement cost for body control module falls between $500 and $700 for parts and labor, while the repair cost could be anywhere around $300 (for resetting or reprogramming).
However, it is important to note that these quote prices are not the final or actual price you may pay to repair or replace a faulty body control module.
These are estimated average costs, so you may pay higher or lower depending on your location and the mechanic workshop where you’re getting the service done; if you DIY the fix, you could save up to $200, which should have been the labor cost you’d pay at the workshop.
Frequently Asked Questions
Can You Drive With a Bad Body Control Module?
Sure thing! You can drive with a bad BCM if the module just recently went back. In contrast, if the module has been bad for a very long time and has caused other crucial components of the car to start malfunctioning, you may find it difficult – if not impossible – to drive the car.
Can The Body Control Module Reset?
Yes, you can reset the BCM if it’s malfunctioning and everything seems to be working again. Resetting the module is recommended if there’s a glitch; if the module is physically affected, resetting won’t fix anything. Generally, to reset the BCM, you have to disconnect the module for some minutes, then reconnect it. But then, the reset procedure varies by vehicle model and make.
What Happens When BCM Fails?
Multiple dashboard lights may illuminate, and the lights may continuously flicker on and off. Also, the alarm may go off at random intervals, the car’s battery would keep dying faster than usual –after full charges – and most accessories installed in the car would start malfunctioning; these are the common signs that the BCM has failed.
Summarily, what are the symptoms of a bad body control module? Parasitic draw and erratic performance of the car’s accessories are the most common symptom; other relatable signs include check engine light and other dashboard lights coming on.
You can reset, repair, or replace a faulty BCM, which costs between $300 and $700.