BMW 2 Diesel: Glow Plug Woes & Cold Start Nightmares

Hi there! I have some experience with cars and had a very similar issue with my 2020 BMW 3 Series diesel last winter. I feel your pain! The symptoms you describe sound exactly like what I dealt with. My mechanic found a loose connection in the wiring harness going to the glow plug control module. They had to trace the entire circuit, but eventually found and fixed the faulty cable connection. The repair was pretty straightforward, cost me 95 Euro, and solved all those annoying symptoms, the constant preheat light, rough starts, and smoke. Before I share more specifics about my repair process, could you share: Have you scanned for specific error codes? Does the smoke appear more during cold starts? How many miles/kilometers on your car? By the way, if you want a second opinion, I really recommend having a diagnostic scan done at a workshop that specializes in BMW diesels. These preheating issues can sometimes be tricky to diagnose correctly.

Hey, thanks for chiming in! My car has 33348 KM and had its last service about 2 months ago. I did get some error codes from my OBD scanner, all pointing to glow plug circuit issues. And yes, the smoke is definitely worse during cold starts, especially in the morning. Your experience is really helpful, I hadn't considered it could be a wiring harness issue. That's actually a bit of a relief since it sounds less expensive than replacing the entire control module. Did you notice any warning lights coming back after the repair? I'm thinking of taking it to a specialist as you suggested, just want to make sure I get it sorted properly the first time around.

Hey again! Thanks for those details about your BMW. Yeah, after my repair last winter, I can definitely confirm that none of those warning lights ever came back. The fix really was permanent. Just to share more about my experience, my car had around 45000 KM when this happened. When they traced the wiring issue, they actually found some slight corrosion on the connectors too, which they cleaned up during the repair. The mechanic mentioned this is pretty common with these models, especially if you regularly park outside. One thing I forgot to mention in my first reply, before getting it fixed, I also noticed the engine would sometimes have a slight hesitation during acceleration, particularly when the engine wasn't fully warmed up. Did you experience anything like that too? The specialist workshop I went to also did a full system check while they were at it, which I'd recommend. They found a few minor issues that could have developed into bigger problems later on. Honestly, even though my issue was just a loose connection, having that thorough check gave me peace of mind. Let me know how you get on with the repair, I'm curious if your issue turns out to be similar to mine!

Thanks so much for all this detailed info! Actually, yes, I've noticed that same hesitation during acceleration you mentioned, especially on cold mornings. I hadn't connected it to the glow plug issues until now, but it makes total sense. I've just booked an appointment with a BMW specialist for next week. You've really put my mind at ease about this whole situation. The fact that your repair was relatively simple and permanent is exactly what I needed to hear. I was honestly worried I'd be looking at a massive repair bill! I'll make sure to ask them to check the wiring harness and connectors first, and get that full system check you recommended. Better to catch any other potential issues now rather than later. Really appreciate you taking the time to share your experience, it's helped me understand what I might be dealing with. I'll let you know what they find when I get it checked out!