BMW X6 Diesel Cold Start Nightmare: Glow Plug Crisis

Had the same problems with my 2014 BMW X5 35d last winter. Initially thought it was just the cold weather, but those symptoms you described are exactly what I experienced, rough cold starts, black smoke, and those annoying warning lights. Took it to the garage and turned out the glow plug wiring harness was corroded, plus two of the glow plugs were shot. The connector pins were also damaged from moisture getting in there. The control module itself was actually fine in my case. It was a pretty serious issue since bad glow plugs can lead to starting problems and engine damage if left unfixed. They had to replace the whole wiring harness and all six glow plugs to be safe. My advice is don't wait on this, those failed emissions and smoke mean something's definitely wrong with the combustion. Took about a day to fix at the shop. Car's been running great since then, starts perfectly even in cold weather. Just make sure you get a proper diagnosis first since these symptoms can sometimes point to injector issues too.

Hey there, thanks for sharing your experience! Really helpful to hear it was just the wiring harness and glow plugs in your case. I've got an appointment scheduled for next week to get mine checked out. Just wondering, do you remember roughly how much you ended up paying for the whole repair? Also, has everything stayed running smoothly since then, or have you noticed any other issues pop up? Been a bit anxious about potential hidden problems.

Hey again! Great to hear back from you. Just wanted to give you a quick update since I dealt with my X5's glow plug problems. Turns out my situation was different from yours, in my case, the mechanic found it was actually just the glow control unit that was faulty. Much simpler fix than what I went through before! Only cost me 95 € to repair a bad cable connection to the control unit. Honestly, I was relieved it wasn't as extensive as my previous repair with the wiring harness and plugs. Since getting it fixed, the car's been running like a dream. No more smoke, warning lights are gone, and cold starts are smooth as butter. Haven't had a single issue pop up since. Really glad I got it sorted, these diesels can be sensitive about their glow plugs, but once you get the problem fixed properly, they're super reliable. Hope your appointment goes well next week! Let us know what they find, always good to share experiences with these common issues.

Thanks for the follow-up! Just got back from my mechanic today and wanted to share what happened. He found that three glow plugs were completely dead and there was a nasty oil leak making things worse. Really glad I didn't wait any longer to get it checked out. The repair took about 4 hours, they replaced all six glow plugs just to be safe and fixed the oil leak. The mechanic was actually really good at explaining everything and showed me the old parts. Way better experience than my last garage visit! They also did a full diagnostic scan to make sure there weren't any other hidden issues. Cost me more than your repair, around 400 for parts and labor, but honestly, I'm just happy it's sorted. The car's running incredibly smooth now, no more black smoke, starts right up in the morning, and the warning lights are finally off. Definitely learned my lesson about not ignoring these warning signs! Thanks again for all your help. It's great when you can get solid advice from someone who's been through similar issues.