Diagnostic Code 51

[KCsTJ]

I randomly check for engine codes and last week a DTC 51 pops up on my 97 SE.

51- Oxygen sensor - lean condition indicated

I just love these vague codes...aarg

Anyone have ideas, please post, headed to the tj right now to check 02 connections, and look for vacuum leaks

It seems to run fine, but since this code popped up it's sucking gas like a Hummer .
cuz the PCM is dumping in fuel to compensate for the lean condition.

The 02 sensor is the correct NGK sensor and was replaced only 2000 miles ago.

 

[Chris]

Maybe it’s a different O2 sensor than the one you replaced.

Usually engine codes are something like P0051. I’ve never heard of just 51 before. Are you missing some numbers?

 

[KCsTJ]

Maybe it’s a different O2 sensor than the one you replaced.

Usually engine codes are something like P0051. I’ve never heard of just 51 before. Are you missing some numbers?

My 97 only displays 2 digit codes and that's what was displayed, using the on-off key method.
I'm not sure but I think later model tj's display the 4 digit codes .
I have not used a hand held code reader, maybe that would give more details.

 

[KCsTJ]

Maybe it’s a different O2 sensor than the one you replaced.

Usually engine codes are something like P0051. I’ve never heard of just 51 before. Are you missing some numbers?

The P0051 code is very similar , it says H02S heater control circuit low , bank 2, sensor 1.
Just checked vacuum lines, all ok.

I need to do some more troubleshooting.

I found this while ago... copper wire showing where the 02 sensor wires attach to the 02 connector.
I wrapped with electrical tape temporarily, till I can get a new 02 wire harness.
Where do I look for an 02 wire harness?

 

[Chris]

The only way you'll be able to find a new O2 wire harness is to find one from a wrecked TJ. That doesn't call for a new harness though. I personally would cut the end off, then solder it back together and use heat shrink to cover the exposed wire. That's the proper way to do it if you ask me.

Was Bank 2, Sensor 1 the O2 sensor you replaced?

I think this exposed wires could be causing some issues, especially if they accidentally contact other metal surfaces.

 

[KCsTJ]

The only way you'll be able to find a new O2 wire harness is to find one from a wrecked TJ. That doesn't call for a new harness though. I personally would cut the end off, then solder it back together and use heat shrink to cover the exposed wire. That's the proper way to do it if you ask me.

Was Bank 2, Sensor 1 the O2 sensor you replaced?

I think this exposed wires could be causing some issues, especially if they accidentally contact other metal surfaces.

That is what I'm thinking, 2 open wires close together, could arc or short out and I don't want any electrical issues for sure
Thanks @Chris that's a good idea to cut and solder, I think that's the way to go in this case

And no, did not replace bank 2 sensor 1. My tj just a 4 cyl so only 1 02 sensor upstream that works and I think its fine, now that I'm repairing that melted wiring

 

[Chris]

That is what I'm thinking, 2 open wires close together, could arc or short out and I don't want any electrical issues for sure
Thanks @Chris that's a good idea to cut and solder, I think that's the way to go in this case

And no, did not replace bank 2 sensor 1. My tj just a 4 cyl so only 1 02 sensor upstream that works and I think its fine, now that I'm repairing that melted wiring

Yep, those wires being exposed could very well be the culprit. For what it's worth, I always replace all the O2 sensors at once. It's cheap enough, it's preventative maintenance, and that way you don't have to worry about others going bad shortly after.