BMW 5 Series Diesel Preheating System Warning Signs

I had similar symptoms on my 2016 BMW 3 Series diesel. The preheating system was the culprit. Dealt with this at the garage about 8 months ago. My car had rough cold starts, white smoke, and the glow plug control module was faulty. The technician found corroded connections on the glow plug wiring harness and two failed glow plugs. It was a serious electrical issue that could've damaged the engine control unit if left unchecked. The smoke and failed emissions were directly related to incomplete combustion from the faulty preheating system. The fix involved replacing the glow plug control module, all four glow plugs, and the wiring harness. Took about a day in the shop, but it solved all the symptoms. The engine runs perfectly now, no smoke, smooth cold starts, and passed emissions with no issues. Given your symptoms, I'd say get it checked soon. These issues typically don't resolve themselves and can lead to bigger problems.

Thanks for sharing your experience! That sounds exactly like what I'm dealing with. Really helpful to know it was the preheating system in your case. My symptoms are practically identical. Would you mind sharing how much you ended up paying for the whole repair? Also curious if you've had any other issues pop up since getting it fixed? Just trying to get an idea of what I'm in for, both cost-wise and if I should expect any other related problems. Thanks again for the detailed explanation. Really helps to hear from someone who's been through it!

Hey again! Just wanted to follow up and share some good news, I finally got my 3 Series sorted out! Turns out it was indeed the preheating control unit that was causing all the trouble, just like I suspected. The mechanic found a faulty cable connection, and honestly, it was a much simpler fix than what I originally went through with my car. The best part? It only cost me 95 € to fix the cable connection issue. Way less than I expected, especially compared to what I'd paid before for other repairs. I should have really done this sooner! Since the repair, my car's been running like a dream, no more smoking issues, cold starts are smooth as butter, and no warning lights whatsoever. Such a relief! You might get lucky like me and just need a simple fix rather than a complete system overhaul. Hope this helps give you a better idea of potential costs. Sometimes these issues turn out to be less scary (and expensive) than we think. Let me know how you get on with yours!

What a relief to hear back from you! Just wanted to update you on my situation, I actually took your advice and got my BMW checked out yesterday. You were spot on about getting it done sooner rather than later. Funny enough, my issue was pretty similar but slightly different. The mechanic I found was really thorough and discovered it was mainly the glow plugs that were shot. They also found some minor wiring issues but nothing as serious as yours. The whole thing set me back about 300 bucks, which honestly isn't as bad as I feared. The car's running so much better now, no more smoke, starts up perfectly even when it's cold, and that annoying check engine light is finally off. Such a weight off my shoulders! Thanks again for encouraging me to get it sorted. Sometimes you just need that push from someone who's been there, you know? Really appreciate you taking the time to share your experience. It definitely helped me make the right decision instead of putting it off any longer!