1. Verify Bulb Installation and Type:
* Double-check the bulbs: Even though you've replaced them, make absolutely sure the new bulbs are correctly seated and the contacts are clean. A slightly loose connection can prevent the light from working.
* Correct Bulb Type: Ensure you used the correct type and wattage of bulb specified in your owner's manual. Using an incorrect bulb can blow a fuse or damage the wiring.
2. Locate the Fuse (It's likely NOT a dedicated fuse):
BMWs often don't have individual fuses for every single light. The license plate lights are usually part of a larger circuit. Check your owner's manual for the fuse box diagrams. Look for fuses related to:
* Tail lights: License plate lights are frequently on the same circuit as the tail lights.
* Rear lights: A more general fuse covering the rear of the car's lighting.
* Interior lights: Sometimes, a single fuse covers multiple interior and exterior lights, including the license plate lights.
3. Check the Wiring and Connectors:
* Wiring harness: Inspect the wiring harness leading to the license plate lights for any damage, cuts, or corrosion. Pay close attention to the connectors at both ends of the harness. A broken wire or a corroded connection is a common cause.
* Ground connection: A poor ground connection can also prevent the lights from working. The ground wire might be corroded or loose. Trace the ground wire from the light housing to ensure it's securely connected to a clean metal surface on the car body.
4. Test for Power at the Lights:
* Use a multimeter: With the ignition switched on, use a multimeter to test for power at the license plate light sockets. You should have 12V at the terminals when the lights should be on. If no power is present, the problem is upstream (before the light).
* Test light: If you don't have a multimeter, you can use a test light (a simple device with a bulb and a probe) to check for power.
5. Check the Light Switch and Related Components (Less Likely, but Possible):
* Light switch: While less likely, a faulty light switch could prevent power from reaching the license plate lights. This would affect other rear lights as well.
* Central electrical control module: In some rare cases, a problem with the car's central electrical control module (or a similar module) could cause this issue. This is a more advanced problem and requires a diagnostic scan tool from a professional.
6. Seek Professional Help:
If you've checked all of the above and are still unable to find the problem, it's best to take your car to a qualified mechanic or BMW specialist. They have the diagnostic tools and expertise to pinpoint the issue more effectively. They can also check for any error codes stored in the car's computer.
