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Mercedes GLS Diesel Engine Control Unit Problem

My 2022 Mercedes GLS diesel is acting up. It has almost 95000 km on it. The engine is running poorly, with seriously reduced engine performance. It's throwing an error code about the engine control unit being defective. I'm guessing it's something to do with the vehicle electronics or the control system. Has anyone had similar ECU problems? Could it be something simple before I take it to the dealership?

4 comment(s)

Sounds familiar. I've got a GLS too, and had similar engine performance issues. Error memory also pointed to the computer module. Check your main relay, it could be a cheap fix before you dive into replacing the whole ECU. Is the error consistent, or does it come and go?

Thanks for the tip! Where exactly is the main relay located? Is there a way to test it, or should I just replace it outright? The error is pretty consistent now, it comes on almost immediately after starting the engine.

Location varies, check your owner's manual for the exact location of the main relay. Testing requires a multimeter and some electrical knowledge, so unless you're comfortable with vehicle electronics, I'd suggest just swapping it. If that doesn't fix it, you're probably looking at deeper ECU problems and a workshop visit. They charged me about 120€ in the end.

You were spot on! Replaced the main relay, and the engine is purring again. The error code is gone, and full power is back. Massive thanks for saving me a ton of money and a trip to the dealership!

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