Rifter Exhaust Treatment Malfunction

Whoa, that's a bummer on a newer Rifter. Exhaust issues can be tricky. First thought, have you checked your DEF fluid level? Low DEF can trigger similar symptoms even in a gasoline engine due to shared sensors. Also, any chance you've noticed anything unusual with the EGR valve recently?

DEF fluid is good, I checked that right away. EGR valve – not specifically, no. What would I be looking for there? Could a bad lambda sensor cause all these issues at once?

Okay, good on the DEF fluid check. As for the EGR, rough idling or hesitation could point to a problem. But yeah, a faulty lambda sensor could definitely cause all those symptoms. It messes with the air/fuel mixture, leading to poor combustion, increased emissions, and a rough running engine. If the sensor is gone, the engine light is expected to come on. Given the exhaust smell and leak, I'd say get it to a workshop.

Thanks for the advice. It was indeed the lambda sensor. Workshop diagnosed it quickly. New sensor fitted and all is well. Repair cost 375€.