Code P0138


Mar 20, 2024
Clearwater, FL
Hello everyone,

(Thank you in advance for all the help!)
We're getting a p0138 O2 Sensor 1/2 Circuit High. Is this a critical sensor I should run out and replace ASAP? I've read several different posts and it seems confusing, some which states it's just for emissions and others that state I should just replace all the sensors. Would love some guidance.

TJ 2004 4.0 Sport

I would replace it as soon as you get the chance, simply because the computer will feed the engine extra fuel as a safety precaution of the oxygen sensor isn't working. Odds are you'll end up burning more in fuel than the cost of the sensor itself. It also increases the odds of blowing a catalytic converter, which is more like a $600-1200 part than a $30 one
  • Like
Reactions: futhgar
(I don't know how to close a post sorry) I actually installed the sensor recently and got rid of the code and a lot of bad idling issues I was having, even bad shifting.
Last edited:
  • Like
Reactions: Steel City 06