Can I put a new O2 sensor in front of the cat and hook it up to the cable that goes into the one in the cat. I want to take the cat off for off road use and was wondering if that would screw up engine performance. Do I need to keep that 02 sensor. Will it matter if I put an O2 sensor in the exhaust right before the cat instead of the on after the cat? Please let me know!

 

First of all ....never tamper . That being said, the one in the cat is used to verify the effiency of the first o2sensor.

 

When I first got my XJ, it came from the previous owner without a cat. I welded on an O2 bung and put the sensor in the straight pipe that was in it's place. I passed inspection like that and emissions were fine. No check engine light or anything. After that, I realized I'd rather pay $50 for a cat that $10,000 for a fine for no cat. Since yours is for off road use, just weld in an O2 bung and screw the sensor in.