P0037 and P0138 fault codes

[Flivver250]

P0037 Powertraine H028 Heater control circuit Low (bank 1 sensor 2) and:

P0138 Powertrain
O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

The rig runs fine. I replaced the O2 sensor down on the exhaust pipe. Is there another hidden? I do not have a catalytic converter and as it is a middle east version, not sure it ever did. Any thoughts? I'd love to see that check engine light go away.

 

[Chris]

All TJs in the U.S. should have catalytic convertors, but being as though yours is from the Middle East, it very well may not have one.

First off, what year is yours, and second, how many O2 sensors do you count?

In the U.S., the 97-00 models had two O2 sensors, whereas the 01-06 models had 4 O2 sensors (2 upstream and 2 downstream).

 

[Flivver250]

Mine is a 2003 with middle east specs. I have only found one O2 sensor in the exhaust pipe on the passenger side. I'll look for the others.

 

[Chris]

Mine is a 2003 with middle east specs. I have only found one O2 sensor in the exhaust pipe on the passenger side. I'll look for the others.

So yours doesn't have the two pre-cats on the downpipes?

If it does, there should be two O2 sensors above the pre-cats, and two below them.

However, even if it doesn't have the pre-cats, there should be one O2 sensor up towards the engine (by the headers), and one further down the system (which is the one you must have already found).

There's another one (at least one) hiding that you haven't found yet. I'm guessing that one is the culprit.

 

[Flivver250]

I found an O2 sensor on my forward exhaust manifold, just above where the exhaust pipe connects to it. The rear one has the bung plugged. The O2 sensor connector is not plugged into anything nor can I find the wire to plug it into.

 

[Chris]

I found an O2 sensor on my forward exhaust manifold, just above where the exhaust pipe connects to it. The rear one has the bung plugged. The O2 sensor connector is not plugged into anything nor can I find the wire to plug it into.

There's got to be a plug there for the O2 sensor somewhere.

How long have these codes been going on for? Since you've had the vehicle?

 

[Flivver250]

The previous owner (not the original) said the light was on the whole time. I have had the rig since May, but had the manifold swapped from one from a junkyard. I was not there when the swap occurred so I'll have to find out if the old manifold was plugged. I'm not convinced the connector is there, it it is, it is well hidden.

 

[Flivver250]

BTW, no pre cats or regular cat. I'll probably have to flag down someone with a similar jeep and ask if I can look under the hood. The junkyard guys might be savvy, they play with them every day.

 

[Flivver250]

I spoke to an offroad shop here and the wrench told me everyone removed the cats and sensors from the TJ system for better flow, blah blah blah. He said if it runs fine, leave it, don't spend the $$ to add a catalytic system for no gain. I'd have preferred it in the stock set up, but will live with it for now. I Am not sure where they hid the wiring harness for the cats anyway. Maybe back of the tranny?

 

[94Shaheed]

Hey brother i know this is a long shot but i got the same situation with my jeep , its 04 with full headers and pipes so they only have one hole for the first o2 sensor, and there aren’t any cats on mine so when i went underneath to check i see there is a plug in the wire harness for a second sensor but no hole in the pipes for it. And my car is throwing the same 2 codes like yours . Did you end up figuring it out or did you leave it as is