It wasn't emergency mode. It was one axle brake mode. When the pressure is unequal the valve slides over to one side to shut off the leak, in your case low fluid and air. When it slides over it turns on the light. you can recenter the valve. The thing is when you are bleeding by foot you must recognize that the pedal is going down further than normal and stop when you come to the least resistance any further and you push the valve off center. Not the engineering as they all work that way. It is a lack of knowledge about the design and function of the system. But now you know for the future.The FIX is in!
I got discouraged attempting to figure this out so I took the truck to a local shop for a diagnosis. Tech on site said he has seen this before and is normally able to fix it by opening both back bleeder screws and slamming on the brake a few times to get the pressure reducing valve (...aka: proportioning valve) to open. This failed so he said he felt replacing it would help.
Sure enough, once I had it off the truck it dawned on me to check the ohms of the 2 wire connection point. (see pic) I compared it to one that I procured from a local salvage yard. (see pic) Installed the new (...used but nice) valve and without turning the key on fluid flow to the rear wheels returned!
A normal brake bleeding sequence was completed. Started the truck and the BRAKE warning light went out. Great!
Now I am left thinking that when the fluid in the reservoir got too low, the valve went into emergency mode and stopped allowing fluid to the back wheels where the leak had developed. At the same time the circuit within the valve opened causing the dash light, "BRAKE" and NOT "ABS BRAKE". (Hence the "base brake" fault the dealership scanner saw) My conclusion: The Dodge engineering design is a one time failure of the Prop Valve if a wheel cylinder failure occurs.