Are my O2 sensors bad?

You can reset it by just disconnecting the battery.
I’d try the right o2 sensors first
The seller told me when the engine light came on he replaced "two" 02 sensors and the guy at oreilly said the 2 on the right looked new. i will have to pull rhem to see what brand they are. Probably cheapos.
 
  • Like
Reactions: JMT
Before you spend any money make sure your header is not cracked (you'll hear a ticking, louder when cold) and that the rest of the exhaust bolts are tight, especially before the sensors. There's a chance, albeit small, that a false O2 reading due to an exhaust leak will cause a light. When I first got my Jeep I was out in heavy rain and had to cross a forded area. Shortly after my CEL came on with O2 codes. Turns out the hot exhaust being splashed with cold water shocked some of the bolts looser than they probably already were and caused a leak. Worth a shot and its free.
 
Before you spend any money make sure your header is not cracked (you'll hear a ticking, louder when cold) and that the rest of the exhaust bolts are tight, especially before the sensors. There's a chance, albeit small, that a false O2 reading due to an exhaust leak will cause a light. When I first got my Jeep I was out in heavy rain and had to cross a forded area. Shortly after my CEL came on with O2 codes. Turns out the hot exhaust being splashed with cold water shocked some of the bolts looser than they probably already were and caused a leak. Worth a shot and its free.
I will check that first. Thank you very much for the tip. I sure hope thats it.
 
I will check that first. Thank you very much for the tip. I sure hope thats it.

One thing to remember if you do change your pre/post cat. You can sell them to a recycling company. Most require a receipt for the new ones (to keep people from stealing them) depending on your state and the conditions of the cat you can get good money for them. Lots of valuable metals inside them.

But i agree with the O2 sensors first. In the O2 thread is a video that explains why aftermarket sensors don't work with Chrysler. Its technical but the simple version is the voltage is wrong. It is only a Chrysler thing. I have always used aftermarket in Ford's and Chevrolet's with no problems.
"Its a Jeep thing"
 
I just hope "its a jeep thing" doesnt break the bank. I waited a long time ro buy another jeep. My first was a 73 CJ5 I bought new right out of high school. (Yep, I am old) I looked for 2+ years to find the right LJ and saved up to buy it. I hope this thing isnt a money pit. Its bone stock and I want to put on slight lift and some nice tires and wheels and thats it. If repair cost are too much then there goes my $ for lift and wheels. We'll see. Thanks for the info.
 
I just hope "its a jeep thing" doesnt break the bank. I waited a long time ro buy another jeep. My first was a 73 CJ5 I bought new right out of high school. (Yep, I am old) I looked for 2+ years to find the right LJ and saved up to buy it. I hope this thing isnt a money pit. Its bone stock and I want to put on slight lift and some nice tires and wheels and thats it. If repair cost are too much then there goes my $ for lift and wheels. We'll see. Thanks for the info.

JEEP= Just Empty Every Pocket!

You have an LJ. That's the best of the best! Ol' reliable 4.0, No smart keys or seat heaters. Last of the REAL Jeeps! Im slightly biased of course.
 
There are four on your newer 4.0 TJ, two on early 2000 and older 4.0 engines.
P.S. If you're going to replace O2 sensors I would replace the two upstream O2 sensors which are on top of the two pre-catalytic converters, not the "two on the right" which would be upstream and downstream. The upstream O2 sensors are the two the PCM uses to set the air-fuel mixture and are more likely to be the cause than the downstream O2 sensors which are primarily to monitor the effectiveness of the pre-cats.

I'm still highly suspicious of the pre-cats being the true cause of the problem. Hopefully a pair of NTK O2 sensors takes care of it but be prepared for them to not be the cure as they weren't on my '04.
 
Thats why it took me so long to find the right one. Very coveted jeep. I just hope I can get these bugs worked out. CEL's drive me nuts. I sure appreciate everyone's input from the forum. You guys have already saved me a bunch of money.
 
P.S. If you're going to replace O2 sensors I would replace the two upstream O2 sensors which are on top of the two pre-catalytic converters, not the "two on the right" which would be upstream and downstream. The upstream O2 sensors are the two the PCM uses to set the air-fuel mixture and are more likely to be the cause than the downstream O2 sensors which are primarily to monitor the effectiveness of the pre-cats.

I'm still highly suspicious of the pre-cats being the true cause of the problem. Hopefully a pair of NTK O2 sensors takes care of it but be prepared for them to not be the cure as they weren't on my '04.
What kind of $$ are we talking for precats do yiu have an idea?
 
In the picture of things, this is not a complex or really expensive issue even if you have to replace the cats. I have had my LJ for about a year and while I have had some issues, these Jeeps are so easy to work on. I love the simplicity and being able to work on it myself.
 
In the picture of things, this is not a complex or really expensive issue even if you have to replace the cats. I have had my LJ for about a year and while I have had some issues, these Jeeps are so easy to work on. I love the simplicity and being able to work on it myself.
Thank You very much. You just lowered my blood pressure a bunch. I just got in my lj, started it up and no check engine light?? Time will tell
 
Yep - no reason to get all worked up. Drive it and have fun. These vehicles aren’t for everyone, but I like mine more now than when I first bought it.