GLK NOx Catalyst and Exhaust Leak

I also own a GLK and have had similar emissions issues. The error code suggests a problem with the NOx catalyst's efficiency. An exhaust leak can affect the NOx catalyst's performance, but the relationship isn't always direct. A leak introduces unmetered air, altering the air-fuel ratio and impacting the catalyst's ability to reduce NOx emissions. It's just one possibility though. The catalyst itself might be degrading due to age and mileage. Where is the exhaust leak?

Thanks for the detailed answer. The exhaust leak seems to be near the flex pipe. Does this location make it more or less likely to affect the NOx catalyst?

A leak near the flex pipe is concerning since it's upstream of the NOx catalyst. This could definitely disrupt the emissions readings. Inspect the exhaust system thoroughly to pinpoint the leak's location and severity. Given the age and mileage, the NOx catalyst might also need replacing. Take your car to a qualified shop for a diagnosis.

Thanks for the advice. I took the car to a workshop. The exhaust system leak was the main issue, costing 265€ to fix. After the repair, the error code is gone, and the system seems normal. Thanks again.