I HAVE A 1996 DAKOTA 4X4, REAR BRAKE WAS LOCKING UP AT LOW SPEED. REPLACED FRONT AND REAR BRAKES ALSO MASTER CYLINDER.B LED BRAKES SEVERAL TIMES .NOW I HAVE NO BRAKE PRESSUREV AT ALL AND THE ABS AND BRAKE LIGHTS ARE ON. COULD IT BE THE COMBINATION VALVE?

its either air (still) or a faulty master cyl I'd think...does the pedal ever firm up?

i have pedal pressure when the truck is off
. When i turn truck pedal goes to the floor