Hi All,
Update. I finally had time to continue troubleshooting this weekend. I think my problem is a bad splice on the SKREEM and IC (-) Can Bus lines. I measured the resistance between the 6 modules on the CAN C BUS. I found that both the PCM and the SKREEM have the correct CAN BUS termination resistance (~122 ohms), but I have an open circuit from the CAN C BUS (-) terminals on the SKREEM and the IC. I could have multiple opens, but both those signals go through the S116 splice, so I figure that's the first place I'll look.
More details: to make this measurement I had to take the center console out to get to the SLA connector; I had to remove the instrument cluster to get to the IC connector and the SKREEM; I had to open up the passenger side front wheel well carpet to get to the TCM; remove the CAB connector, and open up the control box to back probe the PCM. I bought a set of back probes off of Amazon, and I must say, they were well worth the $25 bucks I spent on them.
The table below shows the measurements from each pin on the CAN C BUS to each other. Since I left the PCM C4 connector connected to the PCM, I would expect to measure either a short between pins or ~122 ohms. In most cases I got that except on the SKREEM and IC CAN C BUS (-) lines where they were open. I also checked to see if anything was shorted to ground, but they all were open relative to ground.In order to make the measurement between the PCM and any of the modules internal to the cabin, I used about 15 ft of speaker wire with the two speaker wire conductors twisted together at the ends. Even so, the resistance was on the order of 4 ohms. So my PCM measurements are offset by that resistance.
The figure below is from the Crossfire service manual. I drew yellow squares showing which lines are open, and a red oval around the splice I think is my issue. Hopefully I'll be able to find that splice next weekend and it solves my problem. Unfortunately, the manual only indicates that the splice S116 is on the left side of the steering wheel and behind the instrument cluster. Hopefully, it'll be obvious, but I doubt it.
How does this fit in with the symptoms - the IC isn't displaying the gear shift lever position which it gets from the SLA over the CAN BUS. If the PCM can't talk over the CAN BUS, or at least can't talk to the SKREEM, it probably won't let the car crank.