Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

2000 Jeep Cherokee Check Engine Light

I had the vehicle tested and was told it was the O2 Sensor. I replaced the one in front of the cat converter and the light went off for about a week. It came back on again yesterday and I am wondering if I need to change the other sensor or if it could be another problem?

Thanks for your responses.


1 - Maybe. 2 - Yes. You Are “Throwing Parts” At It. The CEL & The Codes That Set It Tell Which Circuit / System Experienced The Fault, Not Necessarily Which Part(s).

Your car can give one of many or many O2 sensor fault codes. What specific code(s) are you chasing?

So who told you the O2 was the problem; a counter guy at AutoZone or something?

The O2s get blamed for a lot of things. The fact that you may have an O2 related code does not mean the O2 is the problem. This is where the diagnostics start.

This is my error code. I am figuring that I should change the lower O2 sensor at this point. Everything else on the vehicle looks solid.

btw, Thank you both for your responses!

From your own source:
A code P0138 may mean that one or more of the following has happened:

* Faulty O2 sensor
* Short to battery voltage in O2 sensor signal circuit
* High fuel pressure (not as likely)

Now if this is a DIY project and you are saving a ton on labor it might be worth changing the other sensor, otherwise if a shop has done the work take the car back and ask them to fix it properly.

Also forgot to ask, is the code still the same?

Hey again,
I replaced upper O2 sensor myself, not paying a place to do a five minute job for me. The code is still the same though. I have to climb under there and change the second one. They are not expensive and might take care of it. I was also told that a bad gas cap has a very small chance of being the problem as well.

I figure once it stops raining here I will replace both items and then see where I need to go from there. This thing has 122k on it. They were due anyways.

But suggestions if those don’t care of it are helpful. If it is a short, I have checked the battery cables and they seem fine. Do I take it to a mechanic or is there something else I should be checking?