David,
Thanks for the continued attempts at helping out.
Today, I visited a car audio et al store (on Venables), which coincidently happened to have a camera in stock which had the same 4 prong male connector.
The rep was decent enough to go out to the truck and hook his camera to my connector. Truck was put in reverse, but still the "No Signal" message occurred. In his opinion, that suggests the issue is not the camera and it's attached cable, but farther upstream, in the cable from the cab etc.
So that leaves me with the next step, to check that wire. Not sure how I am going to do that as that wiring (and connectors) is specific to my set-up and not easily replaceable to confirm if it is in the wire. If you have further suggestions, I am all ears.
Again, thanks much.
Marv