I have a 2001 GMC sierra sle z71 4x4 extended cab 5.3 automatic and all 4 of the brakes are locking up when driving and continue to become increasingly difficult to go until they lock up to the point you can not move the vehicle at all when left to sit for a while 1 to 4 hours the brakes systems becomes operable again then when driven 5 to ten miles locks up again no abs or brake lights come on the dash and no faulty readings when plugged into a diagnostic unit I changed the abs unitcontrol module (the entire unit module and block) to no avail then I bled the right front caliper which released the pressure on the brake system and disconnected the 2 electrical plugs on the abs unit itself and the 2 sensors on the frame rails going to the front hubs in the engine compartment and pulled the main 60 amp fuse out the ABS light came on the dash cluster then drove the truck off and on over the course of 60 miles with no problems then all 4 wheels locked up again I cracked open the master clyinder lines till fluid dribbled out and retightened. No help still locked then cracked open the bleeder on the driver side caliper fluid squirted out and retightened no help then I cracked open the bleeder on the passenger side front caliper fluid squirted out I retightened and that released the pressure on the brake system I drove it for several miles and the brakes slowly locked up again what the hell is going on I do not have much sanity left or how do you disable it altogether
I don't feel the ABS is the problem. Check all rubber hoses going to the brake system. Try this. When they lock up, see if you can release the brake by breaking a bleeder open on the caliper. If you can, that tells me the rubber hose is bad. They break down inside and allow pressure to be forced into the caliper, but there isn't enough return pressure to release it. As a result, the caliper sticks.