BMW 4 Series Air Suspension Failure, Limp Mode Warning

Hi there! I have some experience working on cars. Had a similar issue with my 2014 BMW 3 series last year. The symptoms you're describing sound very familiar, my car was also sitting unevenly with warning lights. Turned out it was a loose connection in the suspension control module wiring. The workshop found that the cable connector had worked itself loose over time and wasn't making proper contact. The fix was pretty straightforward, they cleaned the connector, secured it properly, and recalibrated the system. Total cost was around 95 Euro, mostly labor. Before jumping to conclusions about the compressor, could you share: Does the issue happen right after starting the car or while driving? Any unusual noises from the suspension? Did you notice if it started after hitting a pothole or bump? These details would help identify if you're dealing with the same problem I had. Better to rule out simple electrical issues before replacing expensive parts.

Thanks for sharing your experience! I've got 69459 KM on my car and just had it serviced last month. The issue started out of nowhere while driving on a smooth road, no potholes or bumps involved. There's actually a faint hissing sound coming from the wheel well when the car is parked, which makes me think it might be more than just a loose connection in my case. I'll definitely get it checked for electrical issues first though. The warning lights and reduced power make me a bit nervous about driving it too much. Did your car also have the misaligned headlights when this happened? That's the part that's really throwing me off.

Oh that hissing sound you mentioned definitely rings some bells, had the exact same thing with my BMW! When you described it, it immediately took me back to my experience. Mine started making that noise too, and initially, I thought like you that it might be a simple electrical issue. But here's the thing, that hissing sound usually means you've got an air leak somewhere in the system. In my case, it turned out that while the loose connection I mentioned earlier was part of the problem, I actually had a small crack in one of the air lines too. The crack was causing the system to lose pressure, which explained the uneven ride height and the headlight misalignment (yes, I had that too!). The reduced power mode is actually a safety feature, the car does this to prevent any potential damage when the suspension system isn't working properly. Smart, but super annoying when you're trying to get somewhere! Given what you've described, I'd bet you're dealing with something similar. When they fixed mine, they ended up replacing the damaged air line and checking all the connections. Cost a bit more than just fixing the loose connection, around 400 Euro total, but it solved everything, including the headlight issue. My advice? Get it to a workshop sooner rather than later. That hissing sound means you're losing air somewhere, and continuing to drive it could potentially cause more damage to the system.

Thanks so much for the detailed explanation! That's really helpful, especially knowing about your experience with the air line crack. I was getting worried about potentially having to replace the entire compressor, so this gives me some hope that it might be something less serious. The hissing sound and similar symptoms definitely make me think you might be right. I've actually just called my regular mechanic and booked it in for tomorrow morning. I'll make sure to mention the possibility of a cracked air line and ask them to check all the connections too. Really appreciate you taking the time to explain everything, especially about the reduced power mode being a safety feature, that makes so much sense now! Will probably end up taking a cab to work tomorrow, but better safe than sorry with these kinds of issues. I'll update the thread once I find out what the actual problem is, might help someone else with similar issues down the line. Thanks again for all your help!