CEL came on today with P0138 code

Tigerman

Tigerman

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Hey Guys and Gals,

My TJ threw a CEL code last night. It is a P0138. Even though it seems to be pretty self-explanatory (says O2 sensor circuit, high voltage Bank 1 Sensor 2), I what I wanted to ask you guys if there is anything else besides replacing the O2 sensor(s) that I should be doing. My 1998 has only two sensors right?... wanted to confirm.

Cheers

20181119_060632.jpg
 
:hanged: another dead sensor.

Should be 2. The post cat is under the skid plate. It doesn't look like fun.

But i would replace both if its in your budget.
 
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Yes there are only two O2 sensors on your '98. Make sure to only use an NTK brand sensor, Bosch O2 sensors are notorious for causing problems in Jeeps.

Not guarantee the O2 sensor on your cat is actually bad, the ECM is known for indicating a bad O2 sensor when it's being fooled by something else.

Also, be prepared for the O2 sensor to be a real booger to remove. A ratchet socket made specifically for O2 sensors are made primarily to install O2 sensors, they commonly aren't strong enough to remove one though. I'd use a 7/8" box-end wrench to remove it and you may need a cheater bar on it to break it free. Cut the wire off the top of the sensor so you can get the box-end wrench over it.

If it just won't budge with a wrench, running the engine long enough to get the O2 sensor and the cat HOT may help but be careful as they really get hot!

Watch this long-winded explanation of how to get more leverage against the O2 sensor before heating things up....

 
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Thanks gentlemen!

Ordered NGK/NTK O2 sensors off of amazon, will be here tomorrow. I've used a flare nut wrench before to remove an oxygen sensor, but it did not look as corroded as the ones I am seeing in my Jeep, so thanks for the tips! Will try to warm it up and burn myself a little of course ;)
 
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Replaced both of the O2 sensors today with the NTK ones as recommended :)

The upstream one came off rather easily. I used a 22mm flare nut wrench on it and did not have to extend the handle.

The downstream (the one in the cat) gave me a fight. I warmed up the Jeep as advised, then quickly put a jack under the tranny and removed the skid plate. It did not budge at all to the wrench I used for the other sensor. Extending it, using the second wrench, did not do the trick either. It was just stuck good in there!!
After some thinking, while helplessly lying under the Jeep, I realized that I could actually get an impact socket on it if the wire was cut. So, I cut the wire, got an impact socket on it, used a medium length extension and after a little bit of wiggling managed to get the impact wrench on. Gave it a squeeze and after a little bit of hesitation it came right off.

Job done, error code reset and "me" is a happy camper.

Side note!
I always had this sound induced vibration when taking off in first gear, due to the 6 cylinder engine's natural low tone rumble. Re-tightening the skid plate got rid of it :) So, if you have the same thing, give those bolts a few extra pounds of torque.
 
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It must be that time of year. I got that code and P0137 a few days ago. I've ordered all 4 O2 sensors (NTK) and I'm just waiting for them to get here.
 
Ive been tossing around the idea of changing my upstream 02 sensor. Its original as far as I know. Rear was swapped two years ago during my tummy tuck. Funny thing, I put the new one in and forgot plug it in, drove around for a day and never threw a code.
 
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My downstream sensor throws a code every now and then. I made a valiant attempt when I was replacing the muffler. It passed emissions here in Virginia so I'm just going to sit on my sensors and do the cut wires trick when the code doesn't go away on it's own. Thanks to everyone for all the great information.
 
Jerry Bransford said:
Yes there are only two O2 sensors on your '98. Make sure to only use an NTK brand sensor, Bosch O2 sensors are notorious for causing problems in Jeeps.

Not guarantee the O2 sensor on your cat is actually bad, the ECM is known for indicating a bad O2 sensor when it's being fooled by something else.

Also, be prepared for the O2 sensor to be a real booger to remove. A ratchet socket made specifically for O2 sensors are made primarily to install O2 sensors, they commonly aren't strong enough to remove one though. I'd use a 7/8" box-end wrench to remove it and you may need a cheater bar on it to break it free. Cut the wire off the top of the sensor so you can get the box-end wrench over it.

If it just won't budge with a wrench, running the engine long enough to get the O2 sensor and the cat HOT may help but be careful as they really get hot!

Watch this long-winded explanation of how to get more leverage against the O2 sensor before heating things up....

Click to expand...




Good to know re: those Bosch O2 sensors.

Nice video too on added leverage with 2nd wrench. However that added torque will easily break bolts as I found when removing my seats last week
 
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