How to reset the Battery Management System (BMS) on a BMW 3 Series e90?

Are you a proud owner of a BMW 3 Series e90? If so, you’re probably in love with its sleek design and powerful performance. But, like any high-performance machine, it requires regular maintenance to keep it running smoothly. One crucial aspect of this maintenance is the Battery Management System (BMS).

You might be wondering, “Why is the BMS so important?” Well, it’s the guardian of your car’s battery, ensuring it performs optimally and lasts as long as possible. And sometimes, this guardian needs a reset to keep doing its job effectively.

Don’t worry, resetting the BMS isn’t as daunting as it sounds. In fact, we’ve got a step-by-step guide to help you through it. So, let’s dive in and get your BMW’s battery back to its best!

NOTE: Resetting the BMS is not the same as registering a new battery

How to know if you have a Battery Management System

Your BMW 3 Series e90 may – or may not – be equipped with a Battery Management System (BMS). This system monitors the battery’s state, adjusting the charging process to optimize battery life and performance.

You can tell if your vehicle has a BMS by looking for a small black box connected to the negative battery terminal. If it’s there, that’s your BMS.

The BMS is crucial in preventing problems like overcharging or deep discharging, which can seriously harm your battery’s health. It’s like a personal trainer for your battery, making sure it’s not overworked or underworked, but just right.

According to Battery University, a well-maintained BMS can significantly extend the lifespan of your battery. So, understanding and taking care of your BMS is key to a healthy, long-lasting battery.

When to Reset the BMS

Knowing when to reset your BMS is just as important as knowing how. Typically, you’d want to reset the BMS after replacing the battery, or if you notice any unusual battery behavior.

Signs that your BMS might need a reset include unexpected battery drain, the battery not holding a charge, or the car’s electrical systems behaving erratically. It’s like when your computer starts acting up, and a quick reboot solves the problem.

Remember, these are just guidelines. If you’re unsure, it’s always best to consult with a professional or refer to your car’s manual.

Precautions Before Resetting the BMS

Safety first, always! Before you dive into resetting the BMS, there are a few precautions you need to take.

Firstly, make sure to disconnect any external devices or chargers from your car. This is to prevent any electrical interference during the reset process. It’s like unplugging your computer before you open it up for repairs.

Secondly, ensure your car is in a safe location and turned off before you start. You wouldn’t want to be in the middle of a busy road trying to reset your BMS!

Step-by-Step Guide to Resetting the BMS

Now, let’s get to the main event: resetting the BMS. Don’t worry, we’ll guide you through every step of the way.

First, you’ll need to locate the battery in your BMW 3 Series e90. It’s usually in the trunk, under a plastic cover. Once you’ve found it, disconnect the negative terminal.

Next, wait for about 10 minutes. This allows the car’s electrical systems to fully shut down. After waiting, reconnect the negative terminal. Your BMS should now be reset!

Remember, these are general instructions and might vary slightly depending on your specific model. Always refer to your car’s manual for precise instructions.

Common Mistakes to Avoid

Resetting the BMS is fairly straightforward, but there are a few common pitfalls to watch out for.

Firstly, make sure you disconnect the negative terminal of the battery, not the positive. Disconnecting the positive terminal can cause a spark, which is a safety hazard.

Secondly, don’t rush the process. Make sure to wait the full 10 minutes before reconnecting the battery. It’s like baking a cake – if you take it out of the oven too soon, it won’t be done properly.

If you run into any issues, don’t hesitate to consult with a professional. It’s better to be safe than sorry!

After Resetting the BMS

Once you’ve successfully reset your BMS, you might be wondering, “What now?” Well, the first thing you should do is monitor your battery’s performance.

You should notice an improvement in battery life and overall performance. If not, it might be worth consulting with a professional to see if there are any underlying issues.

Maybe the BMS was not the issue after all, and your battery needs replacement.

Remember, resetting the BMS is just one part of maintaining your BMW’s battery. Regular check-ups and proper care are just as important!


Resetting the Battery Management System on your BMW 3 Series e90 is a crucial part of maintaining your car’s performance and longevity. With our step-by-step guide, it’s a breeze to do, and the benefits are well worth the effort.

Remember, taking care of your car’s battery is just as important as taking care of the car itself. So, keep up with regular maintenance, follow our tips, and your BMW will thank you with smooth, uninterrupted performance.

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