BMW 6D Glow Plug Controller Problems & Cold Start Issues

Hey there! I had a somewhat similar issue with my 2012 BMW 5 diesel (I also owned a BMW 3 before). I have some experience working on cars, but mostly basic maintenance stuff. My symptoms were pretty much identical to yours, constant glow plug light, rough cold starts, and lots of smoke. Took it to my regular workshop and they found it was just a loose connection in the wiring harness going to the glow plug control unit. They had to clean the contacts and secure the connection properly. The whole thing cost me 95 Euro and it's been running perfectly since then. But before jumping to conclusions, could you share: Have you scanned for error codes? Does the smoking get better once the engine warms up? When did these symptoms first appear? These details would help figure out if you're dealing with the same issue I had or something else.

Thanks for the detailed response! I just hit 45792 KM and had my latest service two months ago. The symptoms started appearing gradually over the last few weeks. I did get it scanned, showing error codes related to the glow plug system (P0380). The smoking does improve once the engine warms up, but those first few minutes are pretty rough. Your experience with the loose connection is really interesting, definitely less expensive than replacing the whole control unit! I'll have my mechanic check the wiring first before jumping into more expensive repairs. It makes sense to start with the simpler potential causes. Did you notice any warning signs before your issue became obvious?

Hey again! Glad to help further with your BMW issue. Yeah, thinking back to my situation, I actually did notice some warning signs before the full-blown problem. About a month before the glow plug light started staying on constantly, I occasionally saw it flicker during cold starts. I initially ignored it since it would disappear after a few seconds. Based on the error code you're getting (P0380) and the mileage, it sounds very similar to what I experienced. The gradual onset of symptoms is also familiar, mine started the same way. One thing I forgot to mention: before I got the wiring fixed, I noticed the smoke was particularly bad during acceleration, especially on cold mornings. Just to give you some extra peace of mind, after my mechanic fixed that loose connection, not only did the immediate symptoms go away, but I also noticed better fuel economy. It's been about 18 months since the repair, and I haven't had any related issues pop up. If your mechanic finds it's more than just a wiring issue, don't panic. Even if you need to replace the control unit, it's still cheaper than dealing with potential damage to other components like the turbo or DPF if left unfixed. But definitely start with checking those connections, could save you a bunch of money like it did for me.

Thanks so much for sharing those extra details about the warning signs, that flickering glow plug light you mentioned sounds exactly like what I noticed about three weeks ago! I totally brushed it off too, thinking it was just a unusual glitch. And now that you mention it, the smoke is definitely worse during acceleration on cold mornings. I'm feeling much more optimistic now. I'll get my mechanic to look at those connections first thing tomorrow. The fact that your car's been running great for 18 months after such a simple fix is really encouraging. You've probably saved me from jumping straight to replacing the whole control unit! I'll keep an eye on the fuel economy too once it's fixed, hadn't even thought about that potential improvement. Really appreciate you taking the time to share your experience. I'll probably post an update once I get it sorted out.