O2 sensor or PCM?

[Chumbo]

Currently wrestling with a silly little TJ. (97)

Had O2 sensor codes and rough idle with loss of power before engine reached “closed loop” temps. Replaced O2 sensors (with the ones recommended by the updated O2 sensor thread) and it ran fine. Drove about 1800 miles then bang O2 codes again.

Codes are for “Heater Element Performance Or Rationality Malfunction” and “Input Voltage Maintained Above Normal Operating Range” on both sensors.

I tested the heater on both and upstream measured 5ohm downstream measured 4.8ohm. Don’t have whisker leads to test the voltage on the sensors while running.

Is there a chance that my PCM is just wigging out? Current issue is intermittent rough idle and loss of power while engine is below “operating temp” but it generally seems to right itself shortly after warming up.

 

[Chris]

Currently wrestling with a silly little TJ. (97)

Had O2 sensor codes and rough idle with loss of power before engine reached “closed loop” temps. Replaced O2 sensors (with the ones recommended by the updated O2 sensor thread) and it ran fine. Drove about 1800 miles then bang O2 codes again.

Codes are for “Heater Element Performance Or Rationality Malfunction” and “Input Voltage Maintained Above Normal Operating Range” on both sensors.

I tested the heater on both and upstream measured 5ohm downstream measured 4.8ohm. Don’t have whisker leads to test the voltage on the sensors while running.

Is there a chance that my PCM is just wigging out? Current issue is intermittent rough idle and loss of power while engine is below “operating temp” but it generally seems to right itself shortly after warming up.

Since the O2 sensors are relatively new and you're still experiencing those codes, it's certainly worth looking at the PCM. I'd highly suggest sending it to Mark (@Wranglerfix) to test out. You can find his site at wranglerfix.com. He's the resident PCM expert around here.

Those codes can sometimes indicate a problem with the wiring or connectors that come from the PCM to the O2 sensors, so I'd also highly recommend checking your wiring first for any signs of corrosion or damage. It could also be a good idea to inspect the ground connections as poor grounds can lead to sensor issues. The wiring is one thing that most people look but so often ends up being the culprit in situations like this.

Since you mentioned intermittent rough idle and loss of power before reaching operating temperature, that could indicate that the PCM is not controlling the fuel mixture correctly until the sensors provide proper feedback. If everything else checks out, testing or swapping the PCM could be a valid next step, but keep in mind that it may need to be flashed to match your vehicle's specifications.

If you have access to a multimeter, it could help diagnose the voltage at the O2 sensors while the engine is running, which might give you more insight. But generally, it sounds like you're on the right track, and don’t hesitate to inspect all wiring and connections first. Good luck, and let us know how it goes!

 

[Wranglerfix]

Currently wrestling with a silly little TJ. (97)

Had O2 sensor codes and rough idle with loss of power before engine reached “closed loop” temps. Replaced O2 sensors (with the ones recommended by the updated O2 sensor thread) and it ran fine. Drove about 1800 miles then bang O2 codes again.

Codes are for “Heater Element Performance Or Rationality Malfunction” and “Input Voltage Maintained Above Normal Operating Range” on both sensors.

I tested the heater on both and upstream measured 5ohm downstream measured 4.8ohm. Don’t have whisker leads to test the voltage on the sensors while running.

Is there a chance that my PCM is just wigging out? Current issue is intermittent rough idle and loss of power while engine is below “operating temp” but it generally seems to right itself shortly after warming up.

It could be the computer failing on you. You can send it into us and we can test it for you if you'd like. With that test, we will know 100% if it is pcm related.

 

[Chumbo]

It could be the computer failing on you. You can send it into us and we can test it for you if you'd like. With that test, we will know 100% if it is pcm related.

What would the turnaround time be on that? I can send it in but I’d need it back (faulty or not) before the 24th. If that timeline doesn’t work then I can send it over shortly thereafter.

 

[Chumbo]

Since the O2 sensors are relatively new and you're still experiencing those codes, it's certainly worth looking at the PCM. I'd highly suggest sending it to Mark (@Wranglerfix) to test out. You can find his site at wranglerfix.com. He's the resident PCM expert around here.

Those codes can sometimes indicate a problem with the wiring or connectors that come from the PCM to the O2 sensors, so I'd also highly recommend checking your wiring first for any signs of corrosion or damage. It could also be a good idea to inspect the ground connections as poor grounds can lead to sensor issues. The wiring is one thing that most people look but so often ends up being the culprit in situations like this.

Since you mentioned intermittent rough idle and loss of power before reaching operating temperature, that could indicate that the PCM is not controlling the fuel mixture correctly until the sensors provide proper feedback. If everything else checks out, testing or swapping the PCM could be a valid next step, but keep in mind that it may need to be flashed to match your vehicle's specifications.

If you have access to a multimeter, it could help diagnose the voltage at the O2 sensors while the engine is running, which might give you more insight. But generally, it sounds like you're on the right track, and don’t hesitate to inspect all wiring and connections first. Good luck, and let us know how it goes!

Checked what wiring I could get to without dropping the transfer case. All the engine bay wiring looks clean with no pinches or rubbing. Even stripped back the corrugated sleeve to look for any shorts in there. Nada. I’ll try to coordinate with Mr. Mark. Thanks for the help!!

 

[Chris]

Checked what wiring I could get to without dropping the transfer case. All the engine bay wiring looks clean with no pinches or rubbing. Even stripped back the corrugated sleeve to look for any shorts in there. Nada. I’ll try to coordinate with Mr. Mark. Thanks for the help!!

You're welcome! Mark is very reasonable and he'll rule out for sure whether it's the PCM or not.

 

[Wranglerfix]

What would the turnaround time be on that? I can send it in but I’d need it back (faulty or not) before the 24th. If that timeline doesn’t work then I can send it over shortly thereafter.

The current turnaround time is one to two days.

 

[Link]

Never sent him one but when I ordered one I think I got it in 2-3 days. He ships really quickly.

 

[Chumbo]

Never sent him one but when I ordered one I think I got it in 2-3 days. He ships really quickly.

Gotcha, think I’ll work w/WranglerFix. I appreciate it. Don’t have bough messages to “like” yet.

 

[Chumbo]

The current turnaround time is one to two days.

I’m emailing you now. Thank you.