BMW M4 Remote Key System Complete Failure Fix Guide

Hey, experienced something really similar with my 2013 BMW M3 last summer. The central locking system started acting weird and the key fob became unreliable. Turned out it wasn't actually the antenna, it was a faulty connection in the CAS (Car Access System) module. When I took it to the garage, they found corroded terminals inside the module that were causing intermittent connection issues. They had to clean the connections and replace some wiring. It wasn't a massive repair, but definitely needed a professional diagnosis because these symptoms can point to multiple issues. Before going to the shop, I tried changing the key fob battery, but that didn't solve it. Since you're getting an error code, I'd definitely get it checked by a BMW specialist. This kind of issue can get worse if left unchecked and might leave you stranded if the key recognition fails completely. Make sure they specifically check the CAS module connections, mine looked fine from the outside but had issues internally. It's not a super serious problem if caught early, but it needs proper attention.

Thanks for sharing your experience! That's really helpful to know about the CAS module being the culprit rather than the antenna. I'm definitely gonna get it checked out soon. Would you mind sharing how much the repair ended up costing you? And has everything been working smoothly since they fixed it, or have you had any other electrical gremlins pop up?

Hey again! Just wanted to update you on my M3 situation. Actually, turned out I was wrong about the CAS module in my case, when I finally took it to the mechanic, they diagnosed it as the bumper antenna after all! They fixed it last week, and it was a much simpler repair than I initially thought. Just needed to sort out a dodgy cable connection to the antenna. Cost me 95 € and honestly, it was worth every penny. The central locking is working perfectly now, no more fumbling with the physical key or getting those annoying error messages. Since the repair, everything's been running smooth as butter. No electrical issues whatsoever. The key fob works like new again, even from a decent distance. Looking back, I probably should've gotten it checked sooner instead of assuming it was something more complex. Really glad I could help point you in the right direction, even if my first guess wasn't quite on the money. These BMWs can be tricky with their electrical quirks sometimes!

Wow, thanks for the follow-up! Actually, I just got back from the mechanic myself. You won't believe it, but my issue was super similar to your final diagnosis. The mechanic found a loose connection in the antenna wiring that was causing all the trouble. Got it sorted in about an hour. The repair bill wasn't too bad either, pretty close to what you paid. Such a relief it wasn't something more serious with the CAS module! Now my key fob is working perfectly again, and I don't have to deal with that annoying error code anymore. Funny how we both worried it might be something major, but it turned out to be a relatively simple fix. Really appreciate you sharing your experience, it gave me the confidence to get it checked out instead of putting it off. These luxury cars can be intimidating when something goes wrong, but sometimes it's just the small stuff! Thanks again for all your help. Time to enjoy my properly functioning M4 again!