check engine light with new cat
 

I replaced the cat with a factory replacement with the o2 port at the outlet and installed a trush turbo muffler and tail pipe and now my check engine light comes on after about 5-10miles of driving. I've reset it several times and same thing happens. Is the new cat or muffler affecting the o2 sensor or could it just be bad?? Thanks

What are your codes showing?

https://www.cherokeeforum.com/f2/jee...di-obdii-3341/

Without seeing codes, and assuming the o2 sensor has not been replaced, my guess is either an exhaust leak is screwing with the o2 sensor, or the sensor itself is bad. It may have gotten used to what the old cat was letting thru. The new cat is passing cleaner air, atleast it should be, and may have confused the aging o2 sensor, which is throwing fits.


Just a guess.

The CEL means your engine is about to explode and blow your hood right off your Jeep.

OR

You can actually read your codes and find out what they really say. That's why they are there, to tell you what's wrong with your vehicle. None of us can tell you what's wrong with it, because we can't read your codes through the internet. Your engine's computer can tell you a lot more than we can.

I'm assuming your user name means you have a '96, which would be OBDII. That means you can drop by any local auto parts store like Auto Zone, Advance Auto, O'Reilly, Pep Boys, etc. and ask them to read the codes for you. They'll do it for free. Then they'll look it up in their computer and tell you what the description is.

This is important: WRITE DOWN BOTH THE NUMERICAL CODE AND THE DESCRIPTION, because otherwise you'll forget the exact number, and some codes are similar but slightly different. Bring it back here and post it. Then we can give you advice based on your actual condition that isn't mere speculation.

Did you also replace the O2 sensors when you replaced the cat, or did you just install the old downstream O2 sensor in the new cat's bung? If you kept your old O2 sensor, I would speculate that you had a tired downstream O2 sensor that gave up the ghost when you changed the cat. However, you should not spend money on a new O2 sensor until you actually read your code to know what the actual problem is. It could be something else. It could be completely unrelated and just happened to trip at the same time by coincidence.

The code is PO138 oxygen sensor high voltage bank 1.

The sensor is original it was not replaced when I replaced cat but the check engine light was not on before I replaced the cat. I've heard of aftermarket exhaust causing o2 sensor issues just didn't know if anyone with 4.0l had the same problems.

Same install, same code. Maybe we should install a new o2 since we installed new cats. Downstream o2 doesn't affect fuel trim so it's low on my priority list.

That is the downstream sensor. You got the high voltage code, which means it could be a bad sensor, or it could be an issue with the electrical supply to the sensor. Check your O2 sensor fuse first to see if it's blown, since a blown fuse can give you a heater circuit code. Also, slide up under there and look around to make sure none of the wires going to the sensor are damaged or touching the exhaust or drive shaft.

If you don't see an electrical issue, replace the sensor. That's probably where the problem is, but you want to rule out the fifty cent fixes before jumping to the fifty dollar ones.

Here's why it shouldn't be: You have a light on. It's no big deal. Suppose you get another CEL that IS a big deal. You won't know you have a more serious problem.

OBDII codes are there to tell you when you have a problem with your motor. They can't do that if you're ignoring them.