P0121 o2

[samoedin]

Hey everyone! Im getting o2 sensor code on a 2.4L TJ. How do I know if its the up-stream or the low-stream sensor?

 

[samoedin]

Also I'm getting p0420 for CC which I just order 510006 oem obd II magnaflow universal. Should I replace both sensors?

 

[JPNinPA]

P0121 is a code for the TPS not an O2 sensor.

The P0420 could the cat and sometimes an exhaust leak.

Fix the 121 reset the PCM and see if the 420 code comes back.

 

[samoedin]

Sorry that was p0141

 

[JPNinPA]

141 is post CAT

First check the wiring and connections then inspect the O2. My mini cat failed and the O2 threw a code similar. Inspection on the O 2 I found it D shaped instead of a nice round O shape.

 

[samoedin]

I did and it looked fine. I noticed that my jeep it sounds different and I hear noises coming from under the engine while giving gas also the performance sucks it feels a lil heavy on taking off. I almost have 200k miles on it!!

 

[JPNinPA]

Likely the CAT. Temp remove the front O2 and see if performance improves. You will get a code for the O2 missing but idle and response will improve if the CAT is blocked.
When you do replace O2 s get oem or NTK brand others often cause issues.

 

[samoedin]

I will def try that. Which one should I remove the up or the low?

 

[JPNinPA]

Pre cat. Closer to the engine

 

[samoedin]

I did take it out and drive around the block I couldn't tell a difference bc it was very loud but now I'm getting more codes p132 and p0031!

 

[samoedin]

I just rest it left it running for about 15 min and all codes are gone!!!! While I was resting it I notice a spark plug wire was loose!!

 

[JPNinPA]

Pic of a damaged downstream O2. The cause is the CAT media braking loose and impacting the O2.

O2.

 

[samoedin]

This is really driving me nuts, I just noticed an oil leaking into the spark plugs from valve cover and I'm not getting the cat 420 error code anymore only o2 sensor! I already bought the cat and O2s should I just take care of the valve and o2s and return the cat or just do it all one shot?

 

[samoedin]

O2 sensor is on and off!

 

[JPNinPA]

What do you mean the O2 is on and off? The CEL lite is on and off?


Just some FWIW info:
My CAT was bad at 30-35k different year & engine... But i threw a O2 heater Code for the sensor not the CAT. A friend of mine replaced his CAT and muffler... The CAT was app 125 and he got 80 for the old one at the scrap yard. You have 200k on the Jeep, so the CAT is likely bad or going. So I guess I'm saying I'd change the CAT.

 

[samoedin]

Yes the CEL goes on and off by itself. I will do that.

 

[JPNinPA]

This happens but the fact that it comes back confirms its real. What could be happening is your driving frequency allows the CAT and O2 to stay hot enough to not be sensed as a issue during starts. With three clean starts the CEL will go out. However if you pull the codes it will be there.

 

[samoedin]

I see. Could it also be the oil leak into the spark plugs?

 

[JPNinPA]

Excessive burning oil will clog the CAT. It's the same for constantly running rich from a stuck injector.