CEL Code P0138

[MadDog]

Hey Guys-

So I was driving the KJ this afternoon doing some errands locally and for no reason that I can detect, my CEL came on. The engine didn't stumble, I couldn't feel any misfiring, and she is idling and performing perfectly normal. I only noticed it when I went to take my foot off the gas quick to get on the brake due to local traffic, which is when I think it popped on. So I went to Autozone and got the code read and it's a P0138. Now the guys at Autozone weren't at all helpful after giving me the code, but their little print out lists a few reasons for the light coming on:
BBHO2S12 circuit condition (Heated O2 Sensor Bank BB1 Sensor 2)
1. Oxygen Sensor Defective
2. Fuel System running very rich or lean - check other codes first (no other codes were listed)
3. Engine misfire condition - repair
4. Fuel pressure very high or low-fuel pump or pressure regulator

It's hard to imagine the O2 sensor being defective, as I would think the engine would have other symptoms of failure. It's also hard to believe it could be a misfire, as I would think this would be a repeated event or something I would have noticed (though I guess it is possible that while I was braking it could have misfired and I wouldn't have felt it not demanding any power).

What are your thoughts? I'm not sure if this is something simple that I can fix or whether I should take it into a dealer. It is still under warranty, just passed 20K on it and haven't had any problems on it. Also, I am wondering if this was just a fluke event due to the quick braking maneuver and if I should try clearing the codes myself and seeing if it reappears. How would I do that anyway? Should I try to re-read the codes myself from the console? I have EVIC but can't remember what that sequence was to read the codes out of the odometer display. Any help or advice would be appreciated!

 

[Dave]

P0138 is as you said. Bank 1 sensor 2 is the sensor after the cat on the drivers side. If it were me and it is still under warrenty as you said I would take it back to the dealer and see if it is warranteed. Otherwise put a scanner on it and reset the code and see what happens. But if it comes back you will need to fix it.

Just my thoughts, but I am not a professional mechanic.

Dave

 

[ShafferNY]

x2

Try your dealer first.

I doubt it's a cylinder misfire since you didn't get any misfire codes.

If your 02 sensor crapped out, it may make the PCM run in open loop. I doubt it though.

If it does run open loop, you'll probably only notice a decrease in MPG's. No real performance issues. It may seem like it has a bit more power too.

It could be the 02 sensor crapped out, or one of the wires on it has been comprised(melted, cut, shorted...) Just a random guess.

 

[Dave]

If it was the one before the cat it would affect your gas mileage I thought. The one after the cat monitors the gases exiting. My KJ only runs open loop for about a minute after start up on a cold engine and then goes right to closed loop according to my scangauge anyway.

Anyway to clarify, there are 4 02 sensors all together. 1 before each cat and one after each cat (2 cats).

It could be a loose wire too like Shaffer said.

Hopefully tjkj will chime in with a professional opinion when he sees this thread.

Dave

 

[ShafferNY]

If it was the one before the cat it would affect your gas mileage I thought. The one after the cat monitors the gases exiting. My KJ only runs open loop for about a minute after start up on a cold engine and then goes right to closed loop according to my scangauge anyway.

Dave

That's the way I thought it worked too. I'm not entirely sure though.

I think the two downstream 02's just measure the effectiveness of the CAT.

 

[Powerslave]

Federal warranty on emissions parts is 80,000 miles, regardless of what the dealer gives you. The problem is the LABOR, they will just charge you enough for the part, and the labor...

 

[Dave]

Federal warranty on emissions parts is 80,000 miles, regardless of what the dealer gives you. The problem is the LABOR, they will just charge you enough for the part, and the labor...

That's a good point Powerslave. I forgot about that. I think the Federal emissions warrenty is 8/80,000. I know it covers the cats but I am not exactly sure what elce.

MadDog, you should check with the dealer first as mentioned anyway.

Dave

 

[MadDog]

Thanks for the advice guys, I will call the a local dealer on Monday and make an appointment for my day off. (On a side note, can anybody recommend a local Atlanta dealer? Otherwise I'll just pick a 5-star dealer from the website.)

The part/problem should be covered by my original 3/36 warranty though, should it not? I bought her in 10/06, and at only 20K I know she's still within that warranty range, so that should cover it. And if not, I have one of the extended service contracts for 6/60 anyway, so that should cover that anyway, but now you guys have made me unsure lol.

 

[dschae1]

I think the Federal emissions warranty is 8/80,000. I know it covers the cats but I am not exactly sure what elce.
Dave

What Are Specified Major Emission Control Components?

There are three specified major emission control components,
covered for the first 8 years or 80,000 miles of vehicle use on 1995
and newer vehicles:

* Catalytic converters.

* The electronic emissions control unit or computer (ECU).

* The onboard emissions diagnostic device or computer (OBD).


*** everything else is 2 years or 24k ***

Source: http://epa.gov/otaq/consumer/warr95fs.txt

 

[jeepchic79]

Humm have you changed the plugs lately ? I had that code come up right after i changed my plugs it went away , now i am dealing with a new code ....

 

[tjkj2002]

What Are Specified Major Emission Control Components?

There are three specified major emission control components,
covered for the first 8 years or 80,000 miles of vehicle use on 1995
and newer vehicles:

* Catalytic converters.

* The electronic emissions control unit or computer (ECU).

* The onboard emissions diagnostic device or computer (OBD).


*** everything else is 2 years or 24k ***

Source: http://epa.gov/otaq/consumer/warr95fs.txt

In bold is only for California,the other 49 states the cats are only covered for 8/80.