P0123 Troubleshooting

[Tbird_TJ]

Hey folks,

New to the forum and TJs. Thanks in advance for your help!

Problem:
- Check Engine Light illuminated.
- Received error code P0123
- Replaced TPS with Mopar part. no unusual throttle or rpms observed. Idling at ~700..
- Light still on, same code. Code could not be reset by my mechanic using multiple OBDs
- considered faulty Clock Spring. Butthe horn and cruise controls are operable and we've got no airbag light illuminated.

Threads I've reviewed:

https://wranglertjforum.com/threads/p0113-p0123-and-rough-idle.84757/
https://wranglertjforum.com/threads/throttle-position-sensor-troubleshooting.850
98/

I'd appreciate any suggestions to continue diagnostics and troubleshooting.

Much appreciated,
TBird

 

[TJ Jim]

Did you probe the three wires to see what your ecm is seeing? One wire is ground. One is five volts and the third is a variable voltage between 0-5 volts.

Welcome to the forum. We will help all we can.

 

[Tbird_TJ]

Did you probe the three wires to see what your ecm is seeing? One wire is ground. One is five volts and the third is a variable voltage between 0-5 volts.

Welcome to the forum. We will help all we can.

Thanks for your response.

I have attempted to do so, but my test is partial so far. I tested the voltage in the harness that connects to the TPS. It reads less than 1V on both the power and signal source (0 on the ground). But the harness was disconnected from the TPS at the time. I could not get a reading on the voltage with the harness connected because the access points are buried down in the harness and I was worried I'd damage the connection if I tried to jam the multimeter probes down in there. So I don't know if this helps at all. Needless to say, I was not able to get a reading on how the voltage varies when the throttle is opened b/c of the above access issue.

How do others get a good voltage reading with the harness connected?

 

[Wildman]

Thanks for your response.

I have attempted to do so, but my test is partial so far. I tested the voltage in the harness that connects to the TPS. It reads less than 1V on both the power and signal source (0 on the ground). But the harness was disconnected from the TPS at the time. I could not get a reading on the voltage with the harness connected because the access points are buried down in the harness and I was worried I'd damage the connection if I tried to jam the multimeter probes down in there. So I don't know if this helps at all. Needless to say, I was not able to get a reading on how the voltage varies when the throttle is opened b/c of the above access issue.

How do others get a good voltage reading with the harness connected?

You use a Back Probe attachment for your multimeter leads.

https://www.amazon.com/Goupchn-Alli...-Diagnostic/dp/B083K5698M/?tag=wranglerorg-20

 

[TJ Jim]

T-pin. Just don’t cross the pins and short out the ecm.

https://www.amazon.com/dp/B0F222KW5R?tag=wranglerorg-20

 

[Tbird_TJ]

You use a Back Probe attachment for your multimeter leads.

View attachment 625578

https://www.amazon.com/Goupchn-Alli...-Diagnostic/dp/B083K5698M/?tag=wranglerorg-20

Thanks for this

 

[Tbird_TJ]

T-pin. Just don’t cross the pins and short out the ecm.

https://www.amazon.com/dp/B0F222KW5R?tag=wranglerorg-20

Thanks for this suggestion.

 

[Wildman]

The T-pins work but the back probe attachments are safer. You can still short out the leads if you're not careful. They are nice to have for many reasons.