Looking for a wire diagram of a 2008 Mercedes Benz c300 sport sedan. I have a p0031 code. The oxygen sensor in question is bank 1, sensor 1, which is the upstream sensor before the catalytic convertor. I have replaced the bank 1, sensor 1 oxygen sensor with a bosch sensor. I don't know the circuit paths to test for good ground. Of course I will test the new harness. Anyone have a diagram?

 

I found three conditions that contributed to the chk engine light.

1] harness to the engine control module (ECM) was damaged. Damaged occurred closest to the harness connector / sensor junction.

2] blown fuse under hood

3] failed oxygen sensor, (Bosch 17016), purchased from third party vendor

Found two wires that were damaged and were held together by two strands. The wires were at an angle such that separation of all but two strands kept the circuit live, causing unstable voltage spikes. If there was significant movement of the wires during normal driving this could account for the voltage spikes and blown fuse.

As a precaution the air intake paths were inspected and cleaned, (i.e., air intakes, air filters, MAF).

I ordered another Bosch oxygen sensor and installed.

Fortunate for me, the check engine light is no more.

There were other rabbit trails that were pursued but the above narrative describes the most relevant activities.

Good luck everyone on your O2 sensor CELs.