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simonstern3

Mercedes CLK diesel preheating lamp and check engine light issue

My 2004 Mercedes CLK diesel is exhibiting some rather irksome behaviour. The preheating lamp refuses to extinguish, and the check engine light has illuminated itself. Further compounding matters, there's noticeable smoke during acceleration. Mileage currently sits at 291526 km. Suspect the glow control unit is at fault, possibly a defective cable or plug connection. Has anyone encountered similar symptoms? Is this a common occurrence? Could a faulty heating element lead to vehicle stalling?

4 comment(s)

juergenschroeder77

Sounds familiar. Though I don't remember the exact year of my CLK, I had a similar headache. The preheating light stayed on, and acceleration felt sluggish. Did you check the control unit itself for any visible damage? Also, how's the cold start? Does it take longer to ignite?

simonstern3 (Author)

Thanks for the quick reply. I appreciate it. I did inspect the control unit, and visually, it appears fine. Cold starts are indeed prolonged. By 'control unit', are you referring to the glow plug control module?

juergenschroeder77

Yes, I was referring to the glow plug control module. Given the prolonged cold start and the other symptoms, it does sound like the module. Honestly, I fiddled around for a bit, but in the end, I took it to a workshop. Probably the easiest solution, to be honest.

simonstern3 (Author)

Appreciated. Replaced the defective glow control unit, which indeed rectified the issue. The root cause was a corroded connection. Total cost: 95€. The preheating lamp now behaves as expected, the check engine light is off, and the smoke during acceleration has ceased. A relatively inexpensive fix, thankfully.

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