[alienator]

My TJ show today check engine light and P0138 code so it looks like new o2 sensor is needed
I had quick look under Jeep and there is 2 sensors;
1 at front and 1 and rear
Anyone know which I should to replace or maybe two of them???any part number???
Btw is Jeep Wrangler 4.0 2001 RHD with coil pack so 2001 onwards
VIN 1J4F4A9S41P365213

Front

Rear

 

[Jerry Bransford]

That particular code is for the downstream (furthest from the engine) O2 sensor which monitors the catalytic converter for proper operation. However, while I normally just suggest replacing only the O2 sensor likely causing the problem, in this case I'll recommend replacing them both with fresh NTK (made by NGK) O2 sensors. The other O2 sensor, closer to the engine, is what monitors the air-fuel mixture and when it goes bad it wreaks havoc with your air fuel mixture which will cause stumbling, missing, and increase petrol consumption. O2 sensors are like spark plugs in that they finally wear out and need to be replaced.

Avoid Bosch O2 sensors which don't work well for some reason in our Jeep engines.

 

[alienator]

Well I noticed increase in mpg.
Any part number from NGK Jerry???

 

[jhanna]

RockAuto.com would probably be my first place to check.

 

[mukluk]

Mopar part numbers for 4.0L oxygen sensors on export Wranglers:
Upstream -- 56041887AA
Downstream -- 56041846AA

 

[alienator]

Thanks [emoji6]

 

[TheBoogieman]

Well I noticed increase in mpg.

Better gas mileage?

 

[alienator]

Yeah 8 - 10 mpg LoL[emoji6][emoji16]

 

[JeepGuyHans]

Hey there all! Just wanted to bring this thread back to life with I hope some useful information. I have a CA emissions 2000 XJ and I just had to replace the O2sensors on it. For us with the CA emissions we have a total of 4 sensors and 3 cats. There is 1 main cat in the usual spot under the passenger compartment, but we also have 2 "pre-cats" up near the engine block where the exhaust manifold goes from 6 to 2 pipes. When I refer to "cat" I am referring to the precats, because that is where all 4 of our sensors reside. So without further ado, here are the O2 part#'s you'll need to do the job: Front pipe pre-cat: 56041212AE, front pipe post cat: 56044215AA, back pipe pre-cat:- 56041213AF, and finally back pipe post-cat:- 56041213AG. I hope this helps!

 

[mmitsch]

Confirming Part Number

That particular code is for the downstream (furthest from the engine) O2 sensor which monitors the catalytic converter for proper operation. However, while I normally just suggest replacing only the O2 sensor likely causing the problem, in this case I'll recommend replacing them both with fresh NTK (made by NGK) O2 sensors. The other O2 sensor, closer to the engine, is what monitors the air-fuel mixture and when it goes bad it wreaks havoc with your air fuel mixture which will cause stumbling, missing, and increase petrol consumption. O2 sensors are like spark plugs in that they finally wear out and need to be replaced.

Avoid Bosch O2 sensors which don't work well for some reason in our Jeep engines.

I just got the PO138 error on my 1999 Jeep Wrangler Sahara. I found this thread and Jerry's response, above.

I think I will replace both of these due to the vehicle age and his logic seemed sound.

Can anybody confirm if the proper NTK Part Numbers are:

Part No. 23099 NTK Downstream
Part No. 23151 NTK Upstream

Let me know and I will get them. If you know a good place let me know.

Also, it seems like replacing these could be terrible (due to age and rust). Do you think I should have our local mechanic put these in for me? Just watched a You-Tube thing and the guy had to use torches, etc. to get them out. :surprise:

Mike