# Jeep Codes



## MickiRig1 (Dec 5, 2003)

A friend of mine is getting codes from auto-zone's scanner. They do not come up with an explanation of the codes. Just comes up with *PO31 and PO51*. It's a 2004 Cherokee - Laredo with the 4.0L. It's just had the O2 sensors replaced and the codes cleared these popped up a week later.


----------



## festerw (Sep 25, 2003)

Here you go

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


----------



## B&B (Nov 4, 2006)

MickiRig1;574745 said:


> A friend of mine is getting codes from auto-zone's scanner. They do not come up with an explanation of the codes. Just comes up with *PO31 and PO51*. It's a 2004 Cherokee - Laredo with the 4.0L. It's just had the O2 sensors replaced and the codes cleared these popped up a week later.


Codes aren't correct Micki, not enough digits. Did you mean P0031 and P0051? Those are both O2 heater related codes. Any other codes?

BTW...All codes (history or pending or OEM specific) may not show up with one of those cheapie Autozone code readers.


----------



## MickiRig1 (Dec 5, 2003)

Thanks B& B and FesterW.
It's a lady at work that has the Jeep. Midas got her for the O2 sensors. Looks like it will go back to them!


----------



## Donny O. (Feb 11, 2005)

if it is for O2 heaters those would be the after cat O2 sensors....unless things have changesd since 96 and it is completely different than my car!! they have pre heaters in them because after the cat the exhaust is not as hot and they need to get to temp quick. basicaly the after cat sensors are jsut there to say if the cat is working or not....it does nothing with tuning or how anything runs......just sets a light if the cat isn't working.....or if the sensor itself is bad. what i'm saying is it can be ran like that with no harm done other than an anoying light!!


----------



## festerw (Sep 25, 2003)

^ or it is possible that they used some cheap universal O2 sensors without the heaters.


----------



## Donny O. (Feb 11, 2005)

festerw;575250 said:


> ^ or it is possible that they used some cheap universal O2 sensors without the heaters.


ya just cant trust anyone anymore!!


----------



## MickiRig1 (Dec 5, 2003)

In our area we have emissions testing. If the check engine light is on they will not even hook it up. I would bet the computer looks for trouble codes and when they were last cleared. I was told you have to have 10 start / drive / stop cycles and 50 miles driven after the codes are cleared to pass.


----------



## B&B (Nov 4, 2006)

Donny O.;575244 said:


> if it is for O2 heaters those would be the after cat O2 sensors....unless things have changed since 96 and it is completely different than my car!!


The pre-cat (primary) O2's are heated as well. Been mandatory since '96.


----------



## Donny O. (Feb 11, 2005)

B&B;575632 said:


> The pre-cat (primary) O2's are heated as well. Been mandatory since '96.


well there ya have it....I have been educated!!


----------

