It’s a common frustration for BMW owners: you go to replace the battery in your 2007 Bmw 328i Key Fob, thinking it’s a simple DIY task, only to find that the key fob stops working correctly afterward. Many owners attempt to replace the key fob battery themselves to avoid dealership costs, sometimes even resorting to soldering new batteries onto the circuit board. However, as you’ve experienced, this process can sometimes lead to unexpected issues.
You mentioned that after replacing the battery in your 2007 BMW 328i key fob, it would start the car, but the remote locking and unlocking functions ceased to work. You even tested the battery voltage and tried reverting to the original battery, but the problem persists. Let’s explore some potential reasons why your key fob might have stopped working after a battery replacement and what steps you can take to troubleshoot the issue.
One of the first things to consider is the battery itself. While you mentioned both the old (VL2020 Panasonic) and new (ML2020 Panasonic) batteries are showing approximately 3V on a multimeter, there could still be subtle differences or issues. Although VL2020 and ML2020 are often interchangeable rechargeable coin cell batteries, it’s worth double-checking the polarity when you installed the new battery. An incorrectly installed battery, even if it seems to fit, can prevent the key fob from functioning correctly.
Another crucial aspect, especially since you mentioned soldering, is the quality of the solder joints. If you performed soldering yourself, examine the solder points closely. A “cold solder joint,” which is a poor connection that can look deceptively like a good solder, can prevent proper electrical flow. Similarly, accidentally creating a solder bridge between different contacts can also cause malfunctions. Carefully inspect the soldering work, ensuring each connection is solid and there are no unintended connections.
Beyond the battery and soldering, consider the possibility of accidental damage to the key fob’s internal components during the battery replacement process. BMW key fobs, especially those for the 2007 328i, contain delicate circuitry. Opening the casing or handling the circuit board without proper care could lead to damage. Look for any visible signs of damage, such as cracked components or bent pins, on the circuit board.
It’s also worth considering if the new key fob shell case you installed might be interfering with the button contacts. While designed to be compatible, sometimes aftermarket cases can have slight variations. Try using the key fob without the new shell case temporarily to see if it makes any difference. This will help rule out any mechanical interference from the new casing.
Although less likely after a simple battery change, there’s a small chance that the key fob might need to be resynchronized with your 2007 BMW 328i. Refer to your BMW owner’s manual for specific instructions on key fob synchronization or pairing procedures. Sometimes, a simple resynchronization can resolve communication issues between the key fob and the car’s receiver.
If you’ve checked all these points and your 2007 BMW 328i key fob still isn’t working for remote functions, it might be time to seek professional help. A qualified automotive locksmith specializing in BMW keys or your local BMW dealership can diagnose more complex issues. They have specialized tools to test the key fob’s RF signal, check for deeper electronic problems, and potentially reprogram the key if necessary.
Troubleshooting a key fob issue after a battery replacement can be tricky. By systematically checking the battery, solder joints, potential damage, casing interference, and considering resynchronization, you can narrow down the possible causes for your 2007 BMW 328i key fob malfunction. If DIY troubleshooting doesn’t resolve the problem, professional assistance is recommended to get your key fob working correctly again.
