ABS Code 21 - Pedal goes to the floor

Please help, brakes are not a option with cars with this much power!!!

I am on my 3rd ABS Teves Mark II actuator assembly from Prior Reman.
When I apply soft brake pedal pressure, the pedal continually sinks to the floor (light braking) and then becomes very hard (seems that only the fronts are working) & the car will stop. If I hammer on the brakes, the pedal is hard and high, then sinks.

Yellow ABS light is always on. All relays and fuses have been checked and/or replaced. I am not losing any fluid. Brakes have been bleed using Fords recommended method right out of their service manual.
I have scanned the computer using a code reader and connection in the trunk & got code 21:

"Main Valve (Disconnect main 2 Pin Plug on Hydraulic Actuator Assembly & measure resistance. 2 to 5.5 Ohms, service cable harness, any other reading replace Actuation Assembly)"

I checked resistance on the switch/sensor attached to the assembly and got 4 Ohms. There is no voltage on the electrical plug, should there be? If so when and how much?

I have looked through a lot of threads and have not been able to find answer.

Any and all comments, questions and feedback is most appreciated,

Thank you,

When you first turn the ignition on, how long does the ABS pump motor run....

Thanks for your help and I will also listen for how long the pump runs.
I tried to empty the accumulator (by pressing the brake pedal 20+ times) but was unable to get that hard pedal feel.

However, I just checked the ground wire that goes from the negative terminal on the battery to the rad saddle, then into a black plastic connection (fuse?).

I think I may have had a bad ground as I was unbolting it, the rad fan came on all by itself (KOEO), which I don't believe I have ever heard on before.
I have cleaned up all the connections, drove it above 25MPH and the Yellow ABS light (on the dash) is still on.

But the pedal feels much stiffer and higher, and does not feel like it is sinking, but that is just driving around in a parking lot. I am gonna drive it home and see what happens (20min drive)

Also, I have already replaced the ignition switch, which I heard maybe responsible for this.

Thanks again !!!!!!!

Do a search for ABS brake problems and you will find quite a bit of info on how to trouble shoot this system....

UPDATE: I have parked the car for the winter, as I now have an extremely hard pedal (barely moves at all) and it takes two feet to hold the car still while in drive or reverse! I just tried KOEO and did not hear the ABS pump motor come on. The car has sat for a few months, battery is fine. Any thoughts??? Thank for the help,

With the ignition switch on, check for 12v power to the brown ABS relay, then check for 12v power to the ABS pump motor....

Sorry i missed this thread way back in may.

Here's what worked on my '91 SC that was throwing a Code 21, I took a 10ga wire and ran it from the grounding bolt on the ABS actuator assembly to the Negative terminal on the battery, and i never seen that code show up ever again..
Like you, i believe, i went connection to connection following the Fords EVTM and found no faults in the wiring either, everything came out good, but running that wire for ground cured the issue.

I don't know if this will help you out in anyway at all, But i "The-Big-E' knows his stuff on these systems so, if he can't get you through it....

beautiful car man I hope you get your issue worked out, what color orange is that if you dont mind me asking. I gotta go get some of those older style rims too, they look way better than the 94 styles imo