BMW 1 Series Alarm System Failure, Complete Fix Guide

Hey there! I have some experience working on cars and had a similar issue with my 2011 BMW 3 Series diesel last year (I also considered a 1 Series at the time). My alarm system was acting up just like yours. Took it to my regular workshop and turns out it just needed a recoding of the alarm system. The indicators weren't synchronizing properly with the locking system. Got it fixed for about 45 Euro, the mechanic just had to reprogram the optical locking sequence. Could you share more details about the error codes you're getting? Also, have you noticed any other electrical issues? This could help pinpoint if it's just a coding issue like mine or something more complex.

Thanks for sharing your experience! I was hoping it would be a simple fix like yours, but I'm getting multiple error codes, mainly related to the control module. The central locking still works fine, but none of the alarm functions do. No other electrical issues that I've noticed, everything else seems normal. My car's at 124696 KM and had its last service about 2 months ago where they didn't mention any potential alarm system problems. A bit frustrated since these BMWs usually have such reliable electronics. Has your fix held up well since the reprogramming?

Hey again! Yeah, my fix has been holding up great since the reprogramming, no issues whatsoever for the past year. But hearing about your control module errors, this does sound more complex than what I dealt with. Even though both our BMWs are from around the same era, the multiple error codes you're getting make me think it might be more than just a coding issue. After my experience, I did some research and learned that the control module itself can fail, especially in these older models. When mine was acting up, I only had that single synchronization error, not multiple codes like yours. Since your central locking is working fine, have you checked the interior motion sensors? On my 3 Series, they're located in the roof liner. When I was troubleshooting mine, I learned these sensors can sometimes fail independently of the main system. Might be worth having those checked specifically. Also, interesting that it wasn't caught during your service two months ago. The system must have failed pretty suddenly. Could there have been any major temperature changes or did you get any electrical work done recently? These systems can be sensitive to that stuff, learned that the hard way with my BMW.

Thanks so much for the detailed response! That's really helpful about the interior motion sensors, I hadn't thought to check those specifically. No recent electrical work or major temperature changes that I can think of, which makes it even more puzzling. The sudden failure is what really threw me off. I just checked the sensors in the roof liner and they look physically fine, but I'm thinking you might be right about this being a control module issue rather than just a coding problem. Bit worried about the repair costs if that's the case, I've heard control module replacements can get pretty expensive on these BMWs. Glad to hear your fix has been reliable though! I'm going to take it to the shop tomorrow and have them specifically check those motion sensors along with the control module. Really appreciate you sharing your experience and the follow-up research you did. It's given me a much better idea of what to discuss with the mechanic. Will probably ask them about the possibility of just the module needing replacement rather than the whole system.