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lennykrueger1

GLA Engine Light and Exhaust Smell

I'm having an issue with my 2021 Mercedes GLA with a gasoline engine. It has 285439 km on it. The check engine light is on, the engine runs rough, and there's a strong exhaust odor. I think it might be an exhaust treatment problem. Could a bad lambda or oxygen sensor be the cause? I want to understand what's happening before I get it fixed.

Summary of the thread

A 2021 Mercedes GLA owner experienced a check engine light, rough engine performance, and a strong exhaust odor, suspecting an exhaust treatment issue. The potential causes discussed included a faulty lambda or oxygen sensor and exhaust leaks. After visiting a workshop, it was confirmed that a bad oxygen sensor was the issue, and replacing it resolved the problem, eliminating the exhaust smell and restoring smooth engine operation.

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4 comment(s)

aaronmueller10

I had a similar thing happen with my 2014 Opel Insignia. Engine light, exhaust smell, and rough idle. It turned out to be the catalytic converter, which failed because of an exhaust leak before it. The engine light came on and off at first. Did you see that? Check the exhaust connections before the catalytic converter.

lennykrueger1 (community.author)

Thanks for the info. You said to check the exhaust connections before the catalytic converter. Can you tell me which connections to check? Besides the smell, what signs of a leak should I look for?

aaronmueller10

On my Insignia, the leak was obvious around the manifold gasket. Look for soot or corrosion around any exhaust joints before the catalytic converter. But a bad oxygen sensor could also cause those symptoms, so a workshop visit is a good idea.

lennykrueger1 (community.author)

I took it to a workshop, and they said it was a bad oxygen sensor. The repair, with the sensor and labor, was 375€. The engine runs fine now, and the exhaust smell is gone. Thanks for the help.

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MERCEDES

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GLA