Replacing the battery in your 2011 BMW 328i key fob should be a straightforward task, but sometimes things don’t go as planned. It’s a common scenario: you get a low battery warning on your dashboard, decide to swap out the old battery for a new one, and suddenly your key fob stops working correctly. You might find that while the key still starts your car, it fails to lock or unlock the doors or operate the trunk remotely. This can be frustrating, especially when you thought you were taking a simple preventative measure.
If you’re experiencing this exact issue after attempting a 2011 BMW 328i key fob battery replacement, you’re not alone. Many BMW owners have encountered similar problems. Let’s explore some potential reasons why your key fob might have stopped working after a battery change and what you can do to troubleshoot the issue.
One of the first things to consider is the battery itself. While you mentioned testing the new battery with a multimeter and confirming a 3V reading, which seems correct for a VL2020 or ML2020 battery, there could still be compatibility issues. It’s good you noted the original battery was a Panasonic VL2020 and you replaced it with an ML2020 Panasonic. These are generally compatible, but it’s always worth double-checking the specifications to ensure they are indeed interchangeable for your specific BMW model and key fob.
Another critical aspect to examine is the battery installation process. Soldering these small batteries can be delicate. If you unsoldered and resoldered the battery terminals, there’s a possibility of a cold solder joint or a break in the connection. A cold solder joint occurs when the solder doesn’t melt and flow properly, resulting in a weak and unreliable electrical connection. This could prevent the key fob from transmitting signals effectively, even if the battery itself is new and functional.
Furthermore, during the process of opening the key fob and handling the internal components, there’s a chance of accidentally damaging other small components on the circuit board. BMW key fobs are compact and contain sensitive electronics. Static discharge, accidental scratches, or even slight bending of the circuit board could lead to malfunction.
Here’s a step-by-step troubleshooting approach to help you diagnose and potentially resolve the issue with your 2011 BMW 328i key fob after a battery replacement:
-
Verify Battery Type and Orientation: Double-check that the replacement battery you used is indeed the correct type (VL2020 or ML2020) and that it is installed with the correct polarity (+ and – sides oriented properly). Even if the battery fits, incorrect polarity will prevent the key fob from working.
-
Inspect Solder Joints: If you soldered the battery, carefully inspect the solder joints under good lighting, ideally with a magnifying glass. Look for shiny, smooth solder joints. Dull, lumpy, or cracked joints indicate a potential cold solder joint. If you suspect a poor solder joint, you may need to carefully reflow the solder to ensure a solid connection. If you are not experienced with soldering, it might be best to seek professional help to avoid further damage.
-
Examine for Damage: Visually inspect the circuit board for any signs of damage. Look for cracks, scratches, or any components that appear to be dislodged or broken. Pay close attention to the area around the battery terminals and any components you might have touched during the battery replacement process.
-
Clean Battery Contacts: Sometimes, even with a new battery, oxidation or debris on the battery contacts can prevent good electrical contact. Use a clean, dry cotton swab or a contact cleaner to gently clean the battery contacts in the key fob and on the battery itself.
-
Reseat Components: Carefully ensure that all components inside the key fob are properly seated. Sometimes, during disassembly and reassembly, a component might become slightly dislodged, leading to connectivity issues.
-
Check Key Fob Programming (Synchronization): While a battery replacement should not typically require reprogramming for basic key functions like locking/unlocking (starting the car usually remains functional as it’s often a separate system), it’s worth trying a key fob synchronization procedure. Refer to your 2011 BMW 328i owner’s manual for specific instructions on key fob synchronization or initialization. This process usually involves a sequence of button presses while inside or near the vehicle.
-
Consider the New Shell Case: You mentioned using a new shell case. While less likely, ensure the new case isn’t physically interfering with the buttons or internal components. Try using the key fob without the new case temporarily to rule out any mechanical interference.
If you have gone through these troubleshooting steps and your 2011 BMW 328i key fob still isn’t working correctly for remote functions (locking/unlocking, trunk), it’s possible that a more complex issue has occurred during the battery replacement, or the key fob itself may have a deeper electronic malfunction unrelated to the battery.
In such cases, it’s advisable to seek professional help. You have a few options:
-
BMW Dealership: A BMW dealership can diagnose key fob issues and offer replacement or reprogramming services. This is often the most expensive option but ensures genuine parts and expert service.
-
Automotive Locksmith: Many automotive locksmiths specialize in key fob repair and replacement. They may be able to diagnose the issue, repair the existing key fob, or provide a new programmed key fob at a potentially lower cost than a dealership. Ensure they have experience with BMW key systems.
-
Specialized Key Fob Repair Services: There are services that specialize in repairing key fobs by mail. This could be an option if you are comfortable sending your key fob away for repair, but ensure you choose a reputable service.
Replacing a 2011 BMW 328i key fob battery should be a simple DIY task. However, when things go wrong, systematic troubleshooting is key. By carefully reviewing each step of the process and considering potential issues, you can often identify the cause and find a solution, or at least determine when it’s time to call in a professional.
