So I bought a 2000 XJ that had a motor swap done with a 95 4.0. I’ve had jeeps on and off all my life and I wanted a new project so I found this for $550 and pulled the trigger. I want it to be able to pass emmission and get it on the road. It has no down pipe or exhaust system just the header for the 95. So obviously I’m getting codes for 02 sensors and im getting four of them 1/1, 1/2, 2/1, 2/2 since the 00-01 has the 2 cats. I’m going to get a down pipe from a scrap yard and have my buddy weld up an exhaust. My question is how can I get away from all four codes? I’ll only have 1 before the cat since it’s a pre 00 header. Pictures for reference on which header it is.

 

If you have a 2000, only the California version (California and states that adopted California standards) had 4 o2 sensors, In 2001 they all did. You might want to take a look at the emission label.

In any case I suspect the pcm is going to be looking for two upstream and two downstream sensors, which were used to monitor the pair of close coupled cats on the California vehicle.
If you're in a state that looks to see if the correct parts are there it might get interesting

 

I’m assuming it had 4 just because it’s getting 4 of the 02 codes. Where exactly might I find the emission label?

 

Should be in engine compartment, on firewall, on your right as your looking at firewall ( so on driver side of vehicle))
If it's a 2000 and looking for four sensors there's a 99% chance it's a California version. In 25 years vehicles move; my 2000 was originally sold in New Jersey, which required California vehicles. ,, moved to Virginia,then West Virginia,, now lives in yet another place.

 

I wonder if I would be able to change the ECU To an earlier year?