can anyone help me on o2 sensor issues? I just bought a 2000 xj and i need help getting the CEL off to pass inspection. I have codes PO130 and PO136 and replaced both o2 sensors corresponding to the codes and still have the light after clearing the codes. The jeep runs significantly better with the new sensors but still has the codes. If i clear the codes they will return as soon as the ignition is turned back on

 

Do you have a code reader able to show live data?
Or else, do you have a multimeter?

 

o2 sensor codes normally take a few min to come back on, and the engine has to be running. You have sensor heater codes that can come from a bad relay or fuse. . Look in the relay/fuse box directly behind overflow bottle. The inside lid shows you what the relays do. See if you can swap the heater relay with something non critical like ac clutch or coolant fan. I dont think the fuses are labeled except for size, see if any are burned out visually as an easy beginning

 

I do in fact have a code reader, I was looking at the o2 sensor voltages on the reader the other day, nothing jumped out at me as out of the ordinary but I also wasn't completely sure what to look out for. I'm going to try and reset the ECM later by unhooking the negative terminal and letting it sit for a little. While I'm in there ill try and clean the grounds to see if anything changes. I'm worried it's a wiring issue as the code returns as soon as the key is in the ignition.

 

It's voltage codes
I find it a bit awkward that the (cleared) codes for the O2 sensors immediately return upon key in ignition without having driven it..

 

Check the wiring to the sensor, mine got decimated by the steering shaft. Here is a picture:

 

So after a bit of digging around, I finally found that fuse #10 on the interior fuse box blows as soon as I put it into reverse (manual trans) and have narrowed it down to a short somewhere in the reverse light wiring or a faulty reverse light switch, which also explains the issue I’ve been having with the purge valve. With the wires to the reverse light switch unplugged the CEL for all three codes turns off. I’m going to replace the reverse light switch tomorrow and see if that fixes the issue.