Hi Mark,
Thanks for your response. I think I've beaten the RCM to death - I've left the ignition on for over ten minutes multiple times while I measured the voltage on all of the RCM and PM connector pins (see below for reference) - the fans never started or rev'd. I've taken the PCM, BCM and RCM connectors off numerous times to check for corrosion, bad/bent pins, broken wires or to reseat, so I don't think I have the same issue as Jonathandugan20 - he had his ECM programmed for new keys, but it seems in the end he didn't put the ECM connector back correctly. Also, you're thinking about 1sweetride - he cleaned connector C207, and his black rectangle disappeared after that - that didn't work for me. I'm starting to think it might be the SKREEM even though I never had the 3 starts and you're out symptom. But checking the resistance between the CAN BUS + and - lines with the PCM C4 connector disconnected, I didn't measure 120 ohms, more like an open. I think what throws me off is that I have a DRB III clone working, and it can talk to the SLA and TCM, so those modules seem okay. The only DTC I read is from the instrument cluster P0600 IC/HVAC comm error - not sure how not talking to the HVAC prevents starting. I thought at one time when I was playing around with the DRB III software I found something saying start enable. Maybe that was in the SKREEM. I'm still not comfortable with the DRB III software, but I see if I can find that again. Maybe I can also check the cam and crankshaft sensors with the DRB III.
-Jerry


Here are the voltages I measured on the RCM and PM with the ignition key in the ON position - everything looks nominal to me:

RELAY CONTROL MODULE A - BLACK 4 WAY
CAV CIRCUIT FUNCTION
1 20BR/VT (EXCEPT SRT) AIR PUMP RELAY CONTROL 12V
1 20GY/BL (SRT) AIR PUMP RELAY CONTROL
2 16RD/BL FUSED ENGINE CONTROL RELAY OUTPUT 12V
3 16RD/DG FUSED ENGINE CONTROL RELAY OUTPUT 12V
4 12RD/WT AIR PUMP RELAY OUTPUT 0V

RELAY CONTROL MODULE B - BLACK 5 WAY
CAV CIRCUIT FUNCTION
1 12RD FUSED B(+) 12V
2 12RD FUSED B(+) 12V
3 14RD/DG FUEL PUMP RELAY OUTPUT 0V (applies 12V when RCM 3E is grounded)
4 14RD FUSED B(+) 12V
5 18BR GROUND 0V

RELAY CONTROL MODULE C - BLACK 5 WAY
CAV CIRCUIT FUNCTION
1 - -
2 - -
3 - -
4 18RD/YL TRACTION SYSTEM RELAY OUTPUT 12V
5 18RD/DG TRACTION SYSTEM RELAY OUTPUT 12V (goes to TCM and SLA)

RELAY CONTROL MODULE D - GRAY 3 WAY
CAV CIRCUIT FUNCTION
1 20YL HORN RELAY CONTROL 12V
2 18PK/RD FUSED IGNITION SWITCH OUTPUT 12V
3 -

RELAY CONTROL MODULE E - GRAY 7 WAY
CAV CIRCUIT FUNCTION
1 16BK/PK FUSED HORN RELAY OUTPUT 0V
2 20RD/WT FUSED IGNITION SWITCH OUTPUT 12V
3 18BL/RD FUEL PUMP RELAY CONTROL 12V (short to grd, draws 0.16A)
4 18BK/DG FUSED B(+) 12V
5 16RD/DG FUSED ENGINE CONTROL RELAY OUTPUT 12V
6 18RD/DG FUSED ENGINE CONTROL RELAY OUTPUT 12V
7 -

PULSE MODULE A - BLACK 5 WAY
CAV CIRCUIT FUNCTION
1 12BK FUSED B(+) 12V
2 20PK/RD SENSOR GROUND 0V (need to connect to grd while turning ignition key to start position)
3 - -
4 - -
5 12BR GROUND 0V

PULSE MODULE B - BLACK 2 WAY
CAV CIRCUIT FUNCTION
1 16VT (A/T) FUSED IGNITION SWITCH OUTPUT 0V
1 20VT (M/T) CLUTCH INTERLOCK SWITCH OUTPUT
2 14PK/RD FUSED IGNITION SWITCH OUTPUT 12V

PULSE MODULE F - 1 WAY
CAV CIRCUIT FUNCTION
1 14VT/WT STARTER SOLENOID OUTPUT 0V (applies 12V when ignition key is turned to start)