Will Disconnected Battery Reset BCM? And How Else Can You Do This?

Disconnecting the battery will reset BCM but this is not the only way to do this. You may also reset it via a good scanner or by pulling a certain fuse out of the fuse box. Also, you need to know for sure that resetting your BCM is needed. One more thing - never do this if you don't have a full understanding of what you are doing!

BCM problems highlights

• Module's importance:High
• Prone to failure:Nounless damaged by water
• Reasons for failure:Water, physical damage, connection problems
• Ways to reset:Only scanner tool
• Sphere of control:Car body, safety, comfort, settings, etc.
• Symptoms of failing:Errors and warnings, functions not working
• Price to repair:$150 - $300
• Price to replace:$550 - $1,100

What's BCM and how does it differ from ECU?

Many car owners think that BCM is just another way to call the ECU - electronic control unit. But the ECU controls the engine and all the connected modules while the BCM (body control module) controls everything else that isn't controlled by the ECU except the transmission. So, the BCM is another control module that may control many different things.

Here's what it can take control of:

• AC and climate control in your vehicle;
• power seats, power rearview mirrors;
• automatic functions like automatic lights or wipers;
• intelligent functions of the vehicle;
• opening and closing windows when programmed.

There are hundreds of other small things that this module controls. And you may not notice its presence in the car up until it stops working and you can't lock the doors or open the windows. When something in your vehicle stops working properly, you immediately get to know more about the BCM.

This is especially true for older cars with high mileage that may have some wiring issues. Their BCMs can cause a lot of problems and drivers need to know some magic to get the modules back to life.

When will you need to reset the BCM?

Resetting any control module is the first step in its repair. Car electronic modules are almost never reliable enough to work for decades without glitching. And once it glitches, your first option is to reset the control module to try and get it back to life. If this doesn't work, you will need some professional help to inspect the vehicle.

So, here are the situations when you may want to reset the BCM:

• your power windows suddenly stopped working;
• nothing happens when you are trying to lock or unlock the doors with the key fob;
• keyless entry system is not working - it also relies on the BCM, in most cases;
• your automatic wipers or auto headlights stopped working;
• the AC doesn't cool the air in the cabin of your vehicle or isn't turned on at all;
• there are error messages on your screen that are telling you about BCM problems.

There are numerous other situations when the BCM may malfunction and cause different minor or major problems with the car. Unfortunately, BCM in modern vehicles has some glitches even more often than the ECU or other modules. One of the reasons is that this module is programmed to complete all the modern intelligent tasks and it gets updated pretty often, so car manufacturers just don't have enough time to test everything well.

Will disconnecting the battery reset your BCM?

The short answer is yes, disconnecting the battery will reset the BCM, but not in all cases. To reset this module, you need to completely cut the power supply to it for several minutes. If you just disconnect the battery, this will lead to the situation when some residual power is still there in the system and it can power the memory chips in the ECU, PCM, and other modules.

Well, for now, you need to know that you can reset your BCM just by disconnecting the battery and following some simple steps after that. If you just disconnect the battery for less than a minute and then connect it back, you will most likely have all the problems back after you start the car.

Proper BCM reset through the disconnected battery

If your BCM is malfunctioning, you can reset it and the easiest way to do it is to cut the electrical power completely for several minutes.

Here's what you should do for this:

• locate the battery of your vehicle - it may be under the hood or in the trunk;
• make sure that everything is off in your car;
• take the cable off the negative terminal first;
• place the cable so that it couldn't touch the terminal of the battery by chance;
• take the cable off the positive terminal;
• get back to your car and turn on something that will consume electricity (headlights, honk, whatever);
• wait for 15 minutes or so;
• make sure you turned off whatever you turned on to use the residual power;
• connect the positive terminal first;
• then connect the negative terminal of the battery;
• check if the problem is gone and the BCM is now working properly.

Now you know that resetting your BCM is only possible if you know how to do it. Just disconnecting one of the terminals for a minute will not reset the module and it will most likely save all its current settings.

Also, you need to know that this kind of resetting the BCM will not help with all possible problems. This will help you if there is a simple software glitch. But if the problem is with the hardware or with some electrical connections, resetting the BCM will not help.

How else can you reset the BCM?

There are three ways you can reset the BCM other than just disconnecting the battery:

1. Unplugging the module

Well, it still requires disconnecting the battery, so I'm not sure which part of this process actually resets the BCM. But the idea is to unplug all the connections from the BCM after you disconnect the battery. You should let it rest for a while and then connect everything back.

2. Using the OBD2 scanner

Not all OBD programs will allow you to easily reset the BCM. Sometimes, you will need professional software or programming skills to do that. But still, you can do this with the help of a good scanner. Find the section that communicates with the BCM, check its codes and possible errors, and then reset it using the functions on your scanner or program.

3. Using professional equipment in the dealership

The dealer can reprogram the BCM, not just reset it. There is a special scan tool that uses exactly the needed programs to test the BCM and see if it works well, or maybe needs replacement. After such a check, you will certainly know if the BCM in your car is still OK or needs replacement.

Of course, this way to check and reset the BCM will cost you quite a lot of money. But you should opt for it when nothing else helps you solve the problem.

What if a simple reset doesn't help you cope with the issue?

It's not that uncommon that after resetting the BCM, the problem is still there and bothers you even more than before. In this way, you should check if you did everything right. Maybe you just didn't reset the BCM correctly and it still holds the old issue.

If resetting the BCM didn't help, you have several possible ways to solve the issue:

Professional inspection. This is a good idea but be ready to pay some money. Although I don't like the idea of going to dealers, inspecting a PCM in any other place may be not efficient due to a lack of specialized equipment.

Replacing the BCM. You can replace the faulty BCM and see if this helps you solve the problem. If you are going to buy the used BCM, you should know that it will require reprogramming before being used in your car.

Reprogramming your BCM. You can go to specialists who reprogram control units in cars and ask for BCM reprogramming. Sometimes, this can also allow you to open some hidden functions of the BCM in your vehicle.

Final thoughts

Now you know what to do if the BCM malfunctions in your vehicle. The easiest way to try and get it back to life is to reset it by disconnecting the battery. Also, you know several other ways to solve the problems that can happen with the body control module in your vehicle. If nothing helps, you should go to the dealership or to a good and trusted repair shop and have the issue inspected and repaired.