have a odd problem, i've not come across before with my brakes. there's a sensor in the proportioning valve, if I connect the wire to it, my brake light comes on instantly. new calipers, new hoses, new rotors, new pads all around. flushed and changed brake fluid. I drive a 89 trans am GTA 5.7L with four wheel disc brakes. the car does not have the 1le option. There are no leaks, and the only physical trouble I can tell is at highway speeds if I brake hard the car wants to pull to the left. Any ideas?

 

From the manual:

"The pressure differential warning switch is designed to constantly compare front and rear brake pressure from the master cylinder and energize the warning light on the dash in the event of a front or rear system failure. The valve and switch are so designed that the switch will latch in the "warning" position once a failure has occurred. The only way the light can be turned off is to repair the failure and apply a pedal force to develop approximately 450 psi line pressure."

Pulling usually indicates a flex hose problem

JamesC