Thanks again Sidewinder.
I looked at the diagnostic port and it matches up perfectly with your drawing. The harness is from a 99 4 door Sport with 4WD.
Keep in mind that you are trying to go from an OBD I protocol to a OBD II protocol, and that the XJ OBD II CCD Bus requires two termination and one bias circuit(s) inorder to function. The instrument cluster in the XJ OBD II has a termination and bias circuit and the PCM has a termination circuit. The OBD II protocol CCD Bus will not work without these circuits.
This I need to work on to gather the information so I understand it. My intail impression was that so long as the diagnostic port was powered, grounded. Has the SCI and the CCD bus from the ECM (C3) it would "talk".
Here is a couple pictures with the offending connector on the right. Then a broader overview of the area of the harness.
Now to be honest and frank what I am doing is retrofitting this harness into a lowly OBD1 YJ.
I chose the XJ harness because the PDC is in about the same position as the YJ/TJ but the ECM being on the drivers side front fender gives me a longer main trunk line for packaging. Plan is to take advantage of the longer wires and mount the ECM in the cabin.
The YJ is set up with stand alone gauges so I need no communication with the ECM in that regard. No AC, cruise etc and best of all in Michigan with are not burdened with emissions laws. Meaning all the emissions stuff can be eliminated.
The plan is to give the ECM the inputs it needs to run and allow it to talk via the diagnostic port via the twisted wire. Everything else will be pared away. Of course the cal that is flashed into the ECM will "block" the missing components/functions so as not to be throwing code after code..
It will be a bit of a challenge integrating the two systems for ignition switch, fuel system, reverse lights, dash power and the like but the YJ is pretty simple and I have rewired it once already.