I got my 2000 xj the day before our stay at home order.... And mvd closed. Great. I need to register it but need emissions done. I have the 2 codes, P0138 and P0141. I'm relatively good at working on vehicles but suck at electronics.

I replaced my rear o2 sensor with a 12 dollar ebay one, like I have with other vehicles...because the wires were torn from the previous owner off-roading. I then read forum posts saying that we need ntk sensors only and felt dumb. I ordered a new ntk for the pre cat sensor and installed it after that

Codes both came back. I believe they refer to the post cat o2 sensor, towards the rear of the Jeep. I tested the sensor for continuity across the white wires and it is fine. The resistance was slightly over 7. I think 4 to 7 is acceptable. I've inspected all wires and they look fine. I checked my fuses, and none are blown. The previous owner said it had an aftermarket exhaust but I don't know what the stock ones look like.

What do you suggest ? An ntk for the rear as well? Test voltage at the harness? I need to register this thing and am frustrated. CELs drive me crazy. Thank you.