your comment on what is occurring is not clear to me.
So if you loose braking @5MPH the brake pedal pulses and the truck continues to keep moving then the sensors are not putting out the proper volts.
I have much experience with this I did the complete deal with this I even took apart the ECBM and did the repair work to the circuit board.
since NO codes and you have a scan tool that has the ability to read those GM ABS codes the wheel sensors must be removed and cleaned and if rust is inside the hub grease the hubs require replacing. the sensors are magnets so the rust will create the sensor volts to drop too low..
the hubs on the exterior rust so the rust will push out the sensor. then the gap between the encoder wheel in the hub is too far away and the sensor volts will drop.
the way to be sure whats up is , you have to disconnect the sensor use a volt meter set it to ac volts and spin the hub assy at a good speed by hand and see if the sensor volts is more than .3vollts AC.. the best reading should be .5volts AC or more. I have found if its .25volts AC or less this will cause your problem.
replacing the sensor is not proper as the sensor may require shims so it is at the proper gap ..if you clean these up and it still produces a lower volts then file the hub where the sensor is mounted then measure again .. if it gets up to .5volts that is the best reading .. .7 volts AC is also good ..
if your do require a new hub do the testing of the sensor volts before install !!!