1996 4.0 AW4, "TPS high input voltage" code P0123

[xjtrailrider]

Long read, bear with me!

This jeep has been trouble free for 20 years. I recently broke a rotor button and when replacing I found play in the distributor shaft, I replaced the distributor. I immediately got a code for the CPS. I replaced the CPS since it was the original with a NTK. Code came back. I read where some new distributors have the drive gear indexed a half tooth off. I pulled my new distributor and that was the issue, I swapped the shaft/gear from my old distributor to the new distributor, problem solved.

It drove perfectly for a week.

Then I get a code for the VSS, my speedometer quite working and the trans would not shift out of 1st gear. I replaced the VSS and pigtail (they don't make the 96 obd2 VSS, I had to use the 98-01 VSS which requires a different connector)

Fixed that issue.

Now I get a code P0123 out of the blue. I have a new NTK TPS on the way but I'm still not convinced that's the issue.

What are your thoughts?

 

[lawsoncl]

If you have a meter, test the TPS voltages by back probing while plugged in. Verify that it has a good ground in particular, because a broken ground to the sensor will cause it to read high. The ground for the TPS is on the side of the block near the dipstick bracket with all the other ground wires. If you haven't already, remove, clean, and reinstall all those grounds.

 

[Tim_MN]

OBD engine sensors can be tested for failure with an $8 - $18 volts/ohms multi-meter from your local hardware store or big box store.

Check engine light trouble codes should focus your diagnostics and testing. Wire harness damage, wire plug corrosion, and dirty/loose ground connections are always good suspects.