For what it's worth my 2000 4.0 has just 2 sensors (no mini cats), and I used Bosch and they've been fine.
Glad I read this post. How long have your Bosch sensors been in?
I just replaced the exhaust system on my '97TJ, from (cracked but welded) header all the way back to the exhaust tip. We put the original sensors (yes, nearly 15 years old and never had a problem) back in, and two trips later they started throwing codes.
First time it happened I got a P0135P and a P0138 (no P). The MIL had lit just after it ran a little rough. BTW, what does that second P mean in the "P0135P"?
Reset the codes (with code reader).
I checked the codes again this morning after coming in to work, because I got a rough run pulling out after the engine had been running about 2 or 3 minutes. No MIL light, but I checked anyway, and got a P0138P.
Anyway, I've got the 1/1 and 1/2 Bosch sensors but haven't installed them yet -- although now I'm wondering if I need to check the part numbers against this thread before I try to install them. Or even trade them in on a different brand, although after reading this last post, I probably won't unless the part numbers are wrong.
I was hoping it would sort itself out after the "newness" of the pipes burned off, but I'm guessing that isn't going to be the case.
I welded up my header for the short term. Much easier. I know I'll have to replace it sooner than later, but with financial commitments lately, I decided to take a chance on it if it only last a few months.
I replaced both my "pre" sensors with Bosch as they were only $19 a piece at the local NAPA and needed to get through emissions. Installation took all of about 10 minutes. Drove to Emissions station the next day, passed, then an hour later the rear sensor started throwing a code again. ...So not even 24hours on that Bosch one. So far, the front Bosch sensor hasn't thrown another code. That was... er.... 4-6 months ago I need to replace that Bosch sensor, but I just haven't bothered to do it yet.
if you go to advance auto parts website and search for oxygen sensors for your 2000 tj, you'll see that they have four parts listed for NTK's. Two of them will say california emissions and two of them won't be.
Thanks 26679cj5 . I guess the ones that say "exc. Calif" are what I need.
I don't have any codes, but my gas mileage has gone done and I can't find any other issues. At 120K miles I am assuming it is time. How necessary is replacing the post cat sensor? I was only planning on replacing the pre-cat one.