Trouble Code P0170

I have a check enging light on a 1998 c230. With a scan tool I found trouble code P0170. This pertains to the oxygen sensor - there are two sensors. Changed out the front sensor and light went away for 3 starts - came back on and same trouble code. Is there something I can do to further test for related problem or just get the other sensor and hope for the best?:banghead:

P0170 Fuel Trim Malfunction (Bank 1) This is the P code for the car. Where did you get the code as an o2 sensor??:rofl: :disappoin

P0170 Fuel Trim Malfunction (Bank 1) This is the P code for the car. Where did you get the code as an o2 sensor??:rofl: :disappoin

Yes, my scan tool shows it part of the fuel trim but specifically says its the O2 malfunction. Also it is operating "open loop" It only has one bank but two sensors. Changed the front sensor and cleared the code temporarily.