2002 Dodge B3500 Van 5.9L - 'No Bus' Diagnostic Code and Gauge Failure After PCM Replacement

I'm experiencing a persistent issue with my 2002 Dodge B3500 Van (5.9L engine). The dashboard displays the 'No Bus' error code, and when I attempt to start the vehicle, it fails to crank properly. All gauges are non-functional—only the odometer flashes before displaying 'no bus'. I recently replaced the Powertrain Control Module (PCM), but after starting the vehicle twice, it stalled immediately and returned to the same error. I've tested each sensor individually by unplugging them one at a time, but the issue persists. A key observation: when I press the ignition key fully in and maintain pressure, the oil pressure and voltage gauges show slight movement. When I release the key, both gauges drop back to zero. This suggests a possible intermittent signal from the key switch or related circuitry. I'm also trying to identify which wire on the sensor plugs provides 5 volts—what is the correct color coding for this power supply? Any guidance would be greatly appreciated.