theresabeck8
Mercedes M Klasse Diesel Reduced Engine Power
Summary of the thread
A 2014 Mercedes M Klasse diesel exhibited reduced engine power warnings, with an error in the engine control unit. The initial suspicion was a faulty main relay. After considering potential causes and solutions, it was confirmed that the main relay in the ECU was indeed faulty, and replacing it resolved the issue.
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4 comment(s)
theresabeck8 (community.author)
System reset as in disconnecting the battery? Yes, I've tried that. Cleared the code, but it returns after a short drive. Anything more involved?
dirkhunter30
I meant a more thorough diagnostic procedure. Since the fault code persists, I think you should see a qualified technician for a proper assessment. The issue might be more than a simple relay malfunction. Intermittent electrical problems are hard to diagnose without the right equipment. I advise against guessing at repairs, as it could make things worse. A defective control system can cause more harm than good.
theresabeck8 (community.author)
Thanks for the input. You were right. The main relay in the ECU was faulty. 120€ later and it's running fine.
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MERCEDES
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MKLASSE
dirkhunter30
I encountered a similar situation with my old 2018 Volvo V90. Reduced engine power and error codes sound like ECU problems. Have you tried a system reset or any diagnostics beyond reading the error memory? Any other electrical issues?