GLC Hybrid exhaust treatment issue

My 2016 Mercedes GLC hybrid is throwing a CEL and running rough with a strong exhaust smell, and I think I can hear a slight leak. Initial scan suggests exhaust treatment malfunction. I suspect a dodgy lambda sensor. Has anyone seen this before on a similar setup? I'm thinking it might be impacting the particulate filter. Could the EGR valve or NOx sensors be involved?

4 comment(s)

I had a similar issue on my previous BMW diesel: engine light, rough running, the works. It turned out to be the oxygen sensor before the catalytic converter. The ECU was getting incorrect readings, messing up the fuel mixture and emissions. It can definitely impact the DPF if left unchecked. Have you checked for any error codes related to the O2 sensor specifically?

The error codes do point towards the lambda sensor, but could a faulty EGR valve cause similar symptoms, potentially triggering the sensor error?

A faulty EGR valve can indeed cause similar symptoms, like rough running and exhaust smells, because it affects the air-fuel mixture and combustion process. However, if the error code specifically points to the oxygen sensor, that's the more likely culprit. I advise getting a diagnostic run at the shop to be sure.

It turned out to be the upstream oxygen sensor, as suspected. I replaced it for 375€. The engine light is off, and it's running smoothly again. No more exhaust smell either.

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