I started a thread on the P0420 code and have since determined that my Cat is bad. I've done a bunch of research, after calling a local muffler shop, and looked up the correct part# according to CARB (I live in lovely California). I got the recommended "universal" replacement CAT converter however..... It doesn't have a place to put my O2 sensor in it like my current (bad) converter does. So my question is: can I just put a threaded O2 bung in the section of pipe after the cat between it and the muffler, and install the sensor there? Will this work?

Edit: I have a 98' XJ Thanks

 

It may but the pcm is gonna be looking for certain perameters. With it not being in the cat it may set that code again since the readings will obviously not be the same

 

should be fine

 

Hmm guess I better call the muffler shop again. Not sure if the post cat readings would be any different if the o2 sensor was just out side the cat outlet or even in the outlet flange itself?? Vs in the post side of the cat.. Not sure a couple of inches in exhaust flow would be that different?l

 

Well the cat basically cleans the exhaust and the pcm reads the o2 sensor to make sure the cat is working properly

 

Most of the universals don't have bung for the sensor but you can put one after the cat like you are suggesting. Should work fine

 

Cool I'll give it a go!!

 

Well I think I figured out why my XJ was throwing the P0420 code. Whom ever had it before me cut the guts out of the Cat.. I pulled the old cat and exhaust off and the Cat was completely hollow. Amazing this thing passed SMOG..... Well I'm gonna replace the Cat and O2 sensor as well as put a new Magnaflow Muffler and Tail Pipe in from performance curve...

 

mine was hollow too when I changed it out - it had blow all the internals out the tailpipe years before

 

Hmm could have been the case with mine however can't help but thing the materials were clogging up my muffler. I replaced everything and welded and o2 bung on the pipe between the cat and muffler. Replaced both o2 sensors and it runs like a top!!

 

Had to do that on mine. The previous owner had removed the catalytic converter . First thing I did when I got the jeep as a matter of fact was to install the new cat.