Download the 2003 Jeep KJ Service Manuals below.
Section 8W has the wiring diagrams. The beginning of the wiring diagrams has the Component Index where you will find the TPS on page 8W-30-22.
You will need to measure the 5 V supply voltage, ground and variation on the throttle output when throttle is moved.
You may have a bad connector or a missing voltage or shorted wiring.
The trouble with that section of wiring is that there are splices tapped onto other wires going off somewhere else so a short on one of those spliced wires can cause your problem.
The 2006 manual has a DTC index on the opening page whereby you can find the P0123 code and you will get taken to a similar logic page but different wire colors. But at least here you are given a flow chart of what to check and what voltages to expect on the different pins.
My 2002 Export CRD suffered a front end impact with a tree.
On this Jeep most of the wires go under the radiator and several of them were damaged there. I have pulled off about 12 bad wires so far over the years and at the moment am chasing a new wiring problem.
Say you have a wire going from point A to B. You need to see that voltage originating at point A finds its way to point B...if not then there is break in this wire so unless you can find the break you need to cut the wire off at both ends and replace it with a new one.
Likewise you need to check that this wire is not shorting to ground or any other wire...with the wire disconnected at both ends measure for leakage from his wire to ground..should be no leakage.
This gets a lot more complicated if one of the splices going off somewhere has a short to ground or some other wire...then you have to cut off all ends of this circuit and replace with new wires....been there done that many times!
Once you have the problem fixed the CEL lamp will only go out after about 5 good On/Off trips.
Have fun….hopefully it is a simple wiring issue.
www.colorado4wheel.com/manuals/Jeep/KJ/
