I've had the check engine light for about two months now throwing a P0432 code. So far I've replaced the gas cap,I did a full tuneup last month. and then barely two days ago the shop I took it to replaced the two O2 senors after the pre-cats. But the cell light came back up this morning for the same issue. Should I replace the other two O2 senors before the precats? (The up stream I believe) or should I take it to a muffler shop to get my cat checked out? Also is there an actual 3rd cat under the truck? I've read on here it's just a resonator????

 

It's a 2001 xj with 137k