PEAK PUTTERS

My jeep is putting on the CEL again for P0420 which is the cat efficiancy code. I had a cracked manifold, replaced it with a new one so hopefully I don't still have an exhaust leak to cause the problem. I think I either have a bad cat or bad O2 sensors. Any way to trick the ECU to think the O2 readings are good?

Black electrical tape usually works for my CEL problems

Seriously though, especially on XJ's, they are tuned to run very lean from the factory. In the interest of piston longevity, you probably need to actually fix the problem so the ECU isn't trying to compensate for the issue and wanting to burn a hole in one of your compression makers...

boo. I don't wanna redo the exhaust right now.