Corrosion in BMW E46 Light Control Module Causing Headlight Fires, Shows Technician

Automotive YouTuber Tyler O’Leary showed what the cause is behind fires in the headlight switch circuit boards of BMW E46s—an issue that has gained infamy among owners of the model, reports The Drive.

Cited as an issue among vehicle owners in BMW forums and Facebook groups for years, faulty Light Control Modules in E46s have been the cause behind what are called “LCM fires.”

The reason for that, as O’Leary shows, is that the LCM circuit boards in the E46 are receiving constant voltage. This allows the lights to turn on without the key in the ignition, but can lead to corrosion if moisture reaches the circuit boards.

Cleaning clogged sunroof drains and maintaining cabin weather seals can help prevent an LCM fire, but the module itself can actually be inspected for corrosion, as O’Leary demonstrates in his video.

In the event of a corroded module, there are a few options, such as replacing the LCM entirely. New ones can be expensive, though, with FCP Euro charging nearly $500 for one.

Additionally, the E46’s LCM is associated with a VIN, meaning a new LCM would likely need to be re-coded before being installed. Installation of a new LCM can also cause a “tamper dot,” a small light next to the odometer meant to indicate incorrect mileage. 

There exists BMW coding software, NCS Expert, that can help program a new LCM, and a separate program called PA Soft can also help with removing a tamper dot, according to The Drive.