My 1999 Nissan Quest with ABS have a wheel lockup at the front left wheel. I have replaced the pads, caliper, rubber hose, and in the process of replacing the master cylinder now.

If I release the hydraulic pressure by cracking the line, the caliper will free up the rotor. I did it at the caliper bleeder, then up the line to the ABS distributing block, then at the line between the master cylinder and the ABS block. At all those points, the locked wheel will free up. So, my conclusion is the master cylinder have a clog preventing the back flow, (right?). What is that brass thing that screws onto the master cylinder? This is where one of the two brake lines from the master cylinder come out of. The stell line goes from the top of this brass thing and goes to the ABS distribution block. The replacement master cylinder don't come withh one and I have to use the original one. Maybe that cound be the problem?
If I use a C-clamp to push the caliper piston back, it is very difficult but can be done, after struggling to remove the caliper off the rotor! If I just leave it overnight, the hydraulic pressure releases a bit and the next morning, I can feel the grip is not as tight.
This happens with and without the engine on. The ABS warning light never came on at any time. You would think the ABS would have a fail mode that would not put a hold on the brakes. When the ABS fails, I thought it would be "removed" from the brake system.

 

I had the same problem whe replaced brake pads. I did all I could just to troubleshoot and discovered that a DAMPER sitting over the master cylinder is STUCK.
I removed the damper and tried to pop the diafragms/***** to move insude the body.
I felt when the become moving since then it happened one more time.
Please note that you do not need this damper. Just drill it through.
The dampre is not used in 2001 and later models.