Need advice regarding o2 resistors/extenders
1997 S420 (USA)
Thank you in advance!
If if it has fresh O2 sensors that are of quality I would start with looking at the signals the front O2 sensors are sending to the ECU. Rich? Lean?
That will provide insight to what is going on. The engine needs to be able to get into closed loop for those codes to go away.
It it would be one thing if you had a code for one downstream O2 sensor. That implies a lazy to failing cat. It is unusual to have both cats having a problem at the same time.
Any help would be appreciated.






