G Klasse oxygen sensor heater failure

A similar issue occurred with my previous BMW a few years ago. Check engine light, higher fuel consumption – the works. Have you inspected the exhaust system wiring harness? On my car, the harness had chafed against the chassis, causing a short. It's like a Christmas tree, one faulty car component affects the others.

Interesting. Was your oxygen sensor itself faulty, or was it solely the wiring? I want to rule out the sensor itself before chasing wires.

In my case, the oxygen sensor was fine. The short in the wiring prevented the heater circuit from functioning, triggering the error code. I would suggest a visit to the workshop. They possess tools for sensor testing that most people do not.

Understood. I appreciate the insight. It ended up being the wiring, as you suspected. Repair cost was indeed 95€.