It’s a common scenario for BMW 328xi owners: you get that low key battery warning on your dashboard and decide to take care of it yourself. Many DIY enthusiasts opt to replace the key fob battery at home, often following online tutorials. However, as you’ve unfortunately discovered, sometimes things don’t go as planned. You replaced the battery in your 2008 Bmw 328xi Key Fob, and now it’s completely unresponsive for locking, unlocking, or even the trunk – even though it still starts the car. You’ve even tried putting the old battery back, but still no luck. Let’s explore why your BMW 328xi key fob might have stopped working after a battery replacement and what you can do to troubleshoot the issue.
One of the first things to consider is whether the new battery is correctly installed. It sounds simple, but polarity matters. Double-check that the positive (+) and negative (-) terminals of the new battery are aligned correctly with the markings inside the key fob case. Even a slight misalignment can prevent the key fob from functioning properly. Also, while you mentioned testing the battery voltage, ensure it’s making good contact within the key fob. Sometimes, the battery terminals in the fob can become slightly bent or lose their springiness, leading to intermittent or no contact.
Another potential issue, especially if you soldered the new battery, is the soldering itself. If you overheated the circuit board during soldering, or if there’s a cold solder joint (a weak connection), it could be disrupting the key fob’s functionality. Carefully inspect your solder points. They should be shiny and smooth, not dull or blobby. If you’re not experienced with soldering, this is a delicate process, and mistakes can happen.
You mentioned using an ML2020 battery instead of the original VL2020. While these battery types might seem similar and even interchangeable in some guides, it’s crucial to verify their compatibility for your specific 2008 BMW 328xi key fob. Although both are 3V lithium batteries, there might be subtle differences in their specifications that could affect performance. It’s always best to use the exact battery type recommended for your key fob to ensure optimal operation.
Sometimes, after a battery change, a BMW key fob might need to be resynchronized with the car. While less common with simple battery replacements, it’s a possibility. The resynchronization procedure can vary depending on the BMW model and year. Consult your 2008 BMW 328xi owner’s manual for instructions on key fob re-initialization or resyncing. It usually involves a sequence of button presses on the key fob and actions inside the car.
Lastly, consider the possibility of accidental damage during the battery replacement process. Key fobs are delicate electronic devices. Static electricity discharge, even if you don’t feel it, can damage sensitive components. If you were working in a dry environment or didn’t take precautions to ground yourself, static could be a culprit. Similarly, physical damage to the circuit board or components inside the key fob during opening or handling could also lead to malfunction.
If you’ve checked all these points – battery polarity, soldering quality (if applicable), battery compatibility, resynchronization procedures – and your 2008 BMW 328xi key fob is still unresponsive, it might be time to seek professional help. A qualified automotive locksmith specializing in BMWs or your local BMW dealership will have diagnostic tools and expertise to pinpoint the exact issue. They can test the key fob’s signal, check for programming problems, or identify any internal damage that might not be visible to the naked eye. While DIY battery replacement can save money, sometimes expert intervention is necessary to resolve complex key fob problems.
