BMW 5-Series Diesel: Glow Plug System Trouble Explained

Hey there! I have some experience working on diesel engines and went through something very similar with my 2015 BMW 3 Series diesel last winter. After seeing those exact symptoms, glow plug light stuck on, rough cold starts, and smoke, I took it to my regular workshop. Turns out it was indeed a faulty connection at the glow plug control module. There was corrosion on one of the plugs causing poor contact. They cleaned the connections and replaced a damaged cable, which sorted everything out. The whole job cost me 95 Euro and has been working perfectly since. Before jumping to conclusions though, could you share which specific fault codes you're getting? Also, how many miles/kilometers are on your car? This would help determine if we're dealing with the same issue or if it might be something else.

Thanks for sharing your experience! I've got 46869 KM on the clock, and my car was serviced just last month. I'm getting the same symptoms you described, really helpful to know about the corrosion issue with the control module. I was worried it might be something more serious, but this gives me hope it could be a relatively straightforward fix. I'll have my mechanic check the connections first before replacing any parts. Did you notice if the smoke reduced immediately after your repair?

Hey again! Yes, the smoke issue cleared up almost immediately after they fixed the control module connections on my BMW. It was like night and day difference, especially during those cold morning starts. The heavy smoke during acceleration completely disappeared within the first few drives after the repair. Since your mileage is pretty similar to what mine was when I had the issue (I was around 50,000 KM), and you're getting identical symptoms, I'm even more convinced it's the same problem. Especially since you mentioned the recent service, sometimes if moisture gets trapped during cleaning, it can accelerate that corrosion on the connections. Just a heads up though, make sure your mechanic thoroughly checks all the connections while they're in there. Initially, mine only cleaned the obvious corroded spots, but we found another dodgy connection a week later. Had to go back and get that sorted too. After they did a proper clean of all contact points and replaced that damaged cable, I haven't had any issues for over a year now. Let me know how it goes, always interested to hear if others with our model have similar experiences!

Thanks for the detailed follow-up! You've convinced me it's worth checking those connections first. I just talked to my mechanic, and he's got me booked in for tomorrow morning. He says he'll do a thorough inspection of all the control module connections and clean any corrosion he finds. Really hoping it's as straightforward as your fix was! I'll definitely make sure they check all the connection points thoroughly, don't want to deal with having to go back like you did. Good tip about watching out for moisture too. Makes sense that my recent service might have contributed to this issue. Will update once I get it sorted. Thanks again for sharing your experience, it's been super helpful in narrowing down what's likely causing my problems. Fingers crossed I'll be back to smoke-free starts soon!