TheoHof
Audi Q7 Diesel: indicator light, black smoke and preheating light
(Translated from German)
Summary of the thread
The 2009 Audi Q7 Diesel is experiencing issues such as black smoke from the exhaust, delayed starting, non-functioning DPF regeneration, and a persistent preheat light. The suspected cause is a faulty pre-glow relay, though defective glow plugs are also considered a possibility. Suggested solutions include checking and possibly replacing the pre-glow relay and glow plugs, and reading the error codes to diagnose the problem accurately.
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5 comment(s)
WolfiJ
That sounds familiar. I had a very similar problem with my 2007 Audi A6. But I'm really not a mechanic, just to emphasize that. In my case, the glow plug was defective due to wear. The workshop then replaced the glow plugs, which fortunately only cost me 200 euros. But I should actually get a better picture of the situation first. How many kilometers has your Q7 already done? And how often do you drive long distances?
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TheoHof (community.author)
Hey, thanks for your answer! My Q7 already has 256871 km on it and I actually often drive longer distances. I will definitely consider your idea with the glow plugs and maybe replace them. Thanks a million for that! Do you think that could also be the reason why the pre-glow light doesn't go out? I look forward to your further assessment.
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AndiFisch
Hey, I had an identical problem with my Ford Mondeo, which had similar symptoms to yours, especially the preheating light not going out. Your theory about the pre-glow relay could well be correct, as it can happen that the relay is defective and no longer controls the pre-glow system properly. In my workshop, they first read out the OBD to check the error codes. They then identified a problem with the preheating system. The mechanics replaced the pre-glow relay and then all the problems disappeared. The replacement cost me around 100 euros, plus a few more euros for troubleshooting. However, it is also possible that your glow plugs are also defective, as WolfiJ has already said, which sounds logical to me. So, have the error codes read out and then you'll know more! Hopefully that will help you. Good luck with it and keep us up to date!
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TheoHof (community.author)
Hey, thanks for your advice! I'll definitely have the pre-glow relay checked then! And of course you're right about the error codes, first find out what's going on. In any case, thank you very much for your tips, that's really a big help!
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Q7
WolfiJ
Well, you've already done quite a few kilometers. Do you remember when the glow plugs were last replaced?
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