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claramueller38

Mercedes S Klasse knock sensor issue

My 2001 Mercedes S Klasse with a gasoline engine is showing some concerning behaviour lately. Specifically, the check engine light is illuminated. I've also observed a noticeable reduction in fuel efficiency and some unevenness in the engine's idling. After running some diagnostics, it seems a knock sensor is defective. I suspect the most likely cause is a defective cable or plug connection to the component. What are your experiences with this issue? I'm looking at about 95€ for what I hope is the eventual repair cost.

Summary of the thread

A 2001 Mercedes S Klasse is experiencing issues with the check engine light, reduced fuel efficiency, and uneven idling, likely due to a defective knock sensor. The suspected cause is a faulty cable or plug connection to the sensor. However, based on similar experiences, the sensor itself may be defective. It is advised to inspect the connections thoroughly but also be prepared for a potential sensor replacement, with professional assistance recommended for accurate diagnosis and repair.

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4 comment(s)

tomwinkler54

Whoa, sounds like a headache! I had a similar issue with my S Klasse – the check engine light was driving me nuts! I'm no expert, but those knock sensors are super important. They listen for engine knocking, which is basically when the fuel-air mixture explodes at the wrong time. That can seriously damage the engine! Did the diagnostics reveal which knock sensor is acting up? Because there are usually two.

claramueller38 (community.author)

The diagnostics indicated the specific knock sensor, yes. However, my main concern revolves around the potential for the cable or plug connection being the root cause, as opposed to the sensor itself failing. I'm trying to avoid replacing the sensor needlessly. Did your issue involve a faulty connection, or was the sensor itself defective?

tomwinkler54

Okay, gotcha. I wish I could tell you it was just the connection, but in my case, it ended up being the sensor itself that was faulty. I'd still check the wiring and connections thoroughly, but be prepared for the possibility of needing a new sensor. Honestly, unless you're really confident in your DIY skills, I'd consider having a workshop take a look. They can properly diagnose the problem and ensure the new sensor is correctly installed. Good luck with this!

claramueller38 (community.author)

I appreciate the information, especially knowing that your experience pointed to sensor failure rather than a simple connection issue. I will proceed with a careful inspection of the connections, but I am now mentally prepared for a sensor replacement. I value your cautious advice and will follow your suggestion by consulting a workshop for a professional assessment and replacement if necessary. Thank you again.

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MERCEDES

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SKLASSE