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michaelhunter49

BMW 6 Series Cold Start Issues, Glow Plug or ECU?

Car won't start

Hi all! I've got a 2004 BMW 6 Series diesel (172k km) giving me some trouble lately. Car won't start sometimes, and it's especially bad when it's cold outside. I suspect it might be the engine control unit acting up. Had a not-so-great experience with my last mechanic, so I'm a bit hesitant to just take it anywhere. Has anyone dealt with similar starting issues in their BMW 6? What was the actual problem and did you find a reliable mechanic who fixed it properly? Thanks in advance!

4 comment(s)


klaus_light1

Hey there! I had a similar issue with my 2007 BMW 5 Series diesel last winter. Initially thought it was the ECU too, but turned out to be much simpler. Had the same symptoms, inconsistent starting, worse in cold weather. Took it to my garage and the problem was just corroded battery terminals and a loose connection. The negative cable wasn't making proper contact, which caused voltage drops. The mechanic cleaned both terminals, replaced the cable clamps, and applied anti-corrosion coating. Definitely wasn't as serious as I'd feared. The battery itself tested fine, but those bad connections were enough to cause all those starting problems. Haven't had any issues since the fix. Worth checking this first before diving into more complex ECU diagnostics. If your battery is original though, might want to have that tested too, as these symptoms can also point to a failing battery. Hope this helps narrow it down a bit.

michaelhunter49 (Author)

Thanks for sharing that experience! That's really helpful and quite similar to what happened with mine. Just wondering, do you remember roughly how much you ended up paying for the terminal cleaning and cable replacement? Also, have you had any other electrical gremlins pop up since getting it fixed?

klaus_light1

Hey again! Yes, glad to help out! The total bill came to 155 € for fixing those cable connections, and honestly, it was money well spent. The mechanic did a thorough job with cleaning, replacing the clamps, and adding that protective coating I mentioned earlier. And you'll be happy to know that since getting it sorted, my BMW hasn't shown a single "Engine Control Malfunction" warning. It starts perfectly every time now, even during those chilly mornings. All those electrical quirks I was experiencing before have completely disappeared. It's such a relief when it turns out to be something relatively simple rather than a major ECU problem, right? Just goes to show sometimes it's the basic stuff we should check first. The car's been running like a champ for months now, and I kick myself for not getting it checked sooner!

michaelhunter49 (Author)

Thanks so much for all those details! You're right, it's such a relief when it's a simple fix. I actually just got back from the mechanic yesterday after taking your advice. Similar story here, they found corroded terminals and a slightly loose connection on the positive cable. Total cost was a bit less than yours, around 120 €, and the car's running perfectly now. Starts right up every time! Can't believe I was stressing about a potential ECU failure when it was just those pesky connections. The mechanic was really honest too, showed me exactly what was wrong instead of trying to upsell me on unnecessary repairs. Finally found a trustworthy shop after my previous bad experiences. They even gave the battery a free health check, turns out it's still in good shape. Thanks again for pointing me in the right direction. Saved me a lot of time and worry!

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