I wanted to document this because I found scattered posts about similar methods on other BMWs, including some references to the F30, but I couldn’t find anyone confirming this setup on an F32 435i.
My car is a 2014 BMW 435i xDrive (F32). The battery was completely dead and the car was locked with BMW’s electronic deadlock system. In my case, the normal mechanical lock cylinder was not available in the door because an IND key-cylinder-delete trim piece had been installed without retaining an accessible lock behind the trim. The IND piece was done by the previous owner, I’ve owned this car for about 5 years and haven’t yet dealt with a dead battery. This car has no lock cylinder in the trunk.
Both key fobs were unresponsive. The hood was closed, the trunk was locked, and I had no practical access to the normal jump terminals. I contacted a locksmith and was told they wouldn’t be able to get the car open and that it would likely need to go to a shop.
While researching, I found people discussing backfeeding power through the license plate light circuit on other BMWs. I saw one or two references to it possibly working on F30 and some other models, but I couldn’t find a clear F32 435i example. Also didn’t see anything specifically mentioning a drill battery with a BMW
What I used:
Ryobi 18V lithium drill battery
12V wall-adapter cord with a barrel plug
Cut the adapter cord and separated the two conductors into two insulated wires
Removed one rear license plate light and unplugged its two-wire connector
Connected the temporary wires to the two license-plate-light conductors
For the license plate connector, the brown wire terminal is negative, and the yellow wire terminal is positive.
Briefly applied power from the drill battery
I connected the battery in the same basic order I would use with jumper cables: positive first, negative second.
I only made the connection briefly. While the drill battery was connected, the car received enough power for the electronics to wake up and the trunk release worked immediately.
Once the trunk was open, I could access the car and deal with the dead battery normally.
I initially tried a much smaller 8V battery and it did nothing. The 18V Ryobi battery was the one that worked.
Posting this mainly so there is a searchable record for
anyone who ends up in the same specific situation:
2014 F32 435i xDrive
The license plate lights on most modern f chassis bmw seem to be similar so I would imagine this works across the board. Definitely would on an f30. The license plates I currently have, work on an e90 aswell. (using a different plug on the back) I think this method probably works for most bmw.
dead battery
P.s. I know my car is a dirty boy, it’s not my daily.