Mercedes CLK O2 Sensor Issue

My 2004 Mercedes CLK with a gasoline engine is showing some symptoms. It has 210248 km on the clock. The check engine light keeps appearing, and the error memory mentions the O2 sensor. I've also seen increased fuel consumption. I suspect a faulty oxygen sensor before the catalytic converter, maybe a defective cable or plug connection. Does this seem likely? I want to avoid a big repair bill, but I also don't want to damage the catalytic converter.

4 comment(s)

It could be the O2 sensor. Is the car running rough? Sometimes a bad sensor throws off the fuel mixture and you'll notice that. It's like when a recipe calls for a teaspoon of salt, but you accidentally dump in a tablespoon.

No, the engine seems to be running smoothly, which is why I suspected the connection first. If the engine was running rough, I'd immediately jump to a mixture problem caused by the sensor itself. Given that it's running smoothly, could a faulty connection still cause the increased fuel consumption and the check engine light?

Yes, a faulty connection could absolutely cause those issues even if the engine runs smooth. The computer is getting bad data from the sensor. I would suggest taking it to a workshop, so they can read the data. You can probably get away with 95€.

Thanks for the insight! I had the O2 sensor and its connection checked at a local garage. Turns out you were spot on it was a corroded connector. They cleaned it, the check engine light is gone, and the fuel consumption seems back to normal. Much appreciated!

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