Hello. As the title states, I'm looking for some advice for o2 extenders or resistors. The car runs great, new o2s were installed, but all 4 codes come back almost immediately. I suspect that the catalytic converters are simply burnt away. I'm content with the way it's running, so looking for as simple of a solution as possible to simply have the codes not be triggered.
1997 S420 (USA)

Thank you in advance!

So you have codes for front and rear O2 sensors?

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.

Somewhat of an update. The codes are P0130, P0150, P0136, and P0156, all of which are O2 CIRCUIT codes. Theoretically, the most logical problem is that there is a problem in power or ground. Is there a fuse that is somehow tied to the O2 sensors? Maybe a common ground they lead to?

Any help would be appreciated.