2000 Jeep Cherokee Check Engine Light

Maintenance/Repairs
,
1

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.



Goose

2

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?
CSA

3

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.

4

http://www.obd-codes.com/p0138

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!

5

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.

6

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

7

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?