Brakes locking on. Help?

[butter4free]

So, I have been searching high and low to no avail for people having the same issue as me.
Backstory: I was driving and had to brake, then my brakes started dragging. Then I had to stop and after that, the brakes seemed to be locked on to the point where I'd have to floor it in first to even move, also my ABS and ESP lights came on. At this point my brake pedal was at the regular height just rock solid. I felt all 4 wheels, which were pretty hot indicating all my brakes were locking up. I released pressure in one bleeder screw, and everything returned to normal, pedal and everything. Scan with vcds reveals code 01435 sender 1 (g201) from brake booster intermittent.
Vcds also shows my resting brake pressure jumping around between 0.33 and 1.0 bar.
Where is this sensor? Or what is it part of? I found a wiring diagram on AllData, but i cannot find the component location. I see nothing electrical on the booster, and the 4 pin pedal position switch seems to be fine.

Any help is much appreciated. Sorry for writing a novel.

[Davdraco1]

The only thing I could think of since you mentioned your resting brake pressure jumping would be a messed up ABS mod. I don't know enough about the electrical side of things. Hope this is some kinda help.

[butter4free]

I'm going to unplug the harness for the abs module, and see what happens. If this is unplugged and the issue still occurs I should be able to rule out an electrical/ABS fault right?