BMW 4 Diesel Won't Start, AdBlue System Troubleshooting

Hey there! I have some experience working on cars, and I actually faced a similar issue with my 2017 BMW 3 Series diesel (320d). When my car showed AdBlue-related errors, it turned out the line from the AdBlue tank to the dosing unit was faulty. Took it to my regular workshop where they diagnosed and fixed it. The whole thing cost me around 250 Euro, but it was worth getting it sorted properly. What engine variant is your 4 Series? Just want to confirm if it's similar to what I dealt with. Also, are you getting any specific error messages on the dash? This would help me share more relevant details from my experience. By the way, if you're interested, I also owned the 5 Series before this one. BMW diesels are great but these AdBlue systems can be tricky sometimes.

Thanks for sharing your experience! My 4 Series has done 48774 KM and had its latest service just 2 months ago. I'm getting the "AdBlue system malfunction" warning, plus the engine management light is on. The symptoms sound really similar to what you described with your 320d. I've been getting somewhat reduced performance too, though it still drives. Going to book it in with my regular workshop, but wanted to understand what I might be dealing with. Did you notice any performance issues before getting yours fixed?

Hey again! Yes, I definitely remember experiencing reduced performance with my 320d before getting it fixed. It's interesting you mention that because it was exactly the same with mine, the car would still drive but felt noticeably sluggish, especially during acceleration. In my case, when I took it to the workshop, they found that the AdBlue line was actually partially blocked, which was causing irregular dosing. That's why I got those similar warning messages you're describing. The reduced performance happens because the engine management system goes into a kind of 'safe mode' to protect itself when the AdBlue system isn't working properly. Since your symptoms are so similar to what I experienced, I'd bet you're dealing with the same issue. Especially since you mentioned having a recent service, sometimes these problems can occur shortly after maintenance if something wasn't connected properly. My mechanic told me this is actually more common than you'd think with these BMW diesel engines. Quick tip from my experience, make sure they check the entire AdBlue system, not just the tank and sensor. In my case, they initially thought it was just a sensor issue, but it turned out to be that blocked line I mentioned. Better to get it all checked properly the first time around. Let me know how it goes when you get it looked at. I'm really curious if it turns out to be the same problem I had!

Thanks so much for all that detailed info, especially about the performance issues! That's really helpful to know it matches what you experienced. I'll definitely mention the blocked line possibility to my workshop when I take it in tomorrow. Makes total sense about the safe mode too, explains why it feels so sluggish during acceleration. You're right about getting the whole system checked. I'll make sure they do a complete inspection rather than just assuming it's a sensor issue. Really appreciate you taking the time to share your experience, it's made me feel much better about the whole situation knowing it's a fixable problem that others have dealt with. I'll update you once I get it sorted. Thanks again for all the help!