UPDATE- The problem was caused by a replacement PCM connector that was mislabeled, so the PCM was not getting any power or ground. Once I sorted that, it worked as it should.
So I have swapped in a 2004 Chevy Gen 3 V8 and 4L80 trans into my Durango. I retained both PCMs. Truck starts and runs fine on the GM PCM, but no gauges work. GM PCM runs the engine and trans, Dodge PCM runs the truck- things such as cruise, gauges, AC. The gauges all operate via CCD bus. I'm getting a CCD bus error. I have the following PCM inputs hooked up:
Power (battery & switched)
Both grounds
Oil pressure sense
Coolant temp sense
Crank sensor (via the GM sensor modified tach output in HPT to try & get the OEM 8 PPR)
Sensor ground tied in to GM PCM
AC connections (request, select)
Brake switch
Cruise control
Vehicle speed (from rear axle)
Fuel level
CCD bus + and - (both show OK continuity from datalink connector)
SCI transmit & receive (both show OK continuity from datalink connector)
Battery temperature
My instinct is the PCM is not "awake" to communicate. Does the ASD relay output (+12V "sense") need to be connected? I was using it to power a relay for an add-on fuse panel.
EDIT-
Here's what the shop manual says about the ASD input:
AUTOMATIC SHUTDOWN (ASD) RELAY SENSE?PCM INPUT
A 12 volt signal at this input indicates to the Powertrain Control Module (PCM) that the ASD has been activated. The ASD relay is located in the Power Distribution Center (PDC). The PDC is located in the engine compartment (Fig. 2). Refer to label on PDC cover for relay location. The relay is used to connect the oxygen sensor heater element, ignition coil and fuel injectors to 12 volt + power supply.
This input is used only to sense that the ASD relay is energized. If the PCM does not see 12 volts at this input when the ASD should be activated, it will set a Diagnostic Trouble Code (DTC).
Thanks for any advice.