I have a 99 c230 kompressor and I have a check engine light on showing a p0170 (Fuel trim malfunction). I have replace the Fuel Pump, Fuel Filter, Fuel regulator, Spark Plugs, and had it check for Vacuume Leak.. It seems that none of these have fixed the problem... Was wanting to know if an o2 sensor would cause this code to come up... Dose anybody have any Ideas...

 

Usual suspect is upper stream 02 sensor. In my case it was.

 

Thanks for your info.. I will try that out and post the final result...

 

Replaced the front o2 sensor and it fixed the problem... Thanks