Trooper LS V6-3.5L (1998)
Brake Proportioning/Combination Valve: Description and Operation
The Proportioning And Bypass (P&B) valve contains two sections, each serving a different function.
The proportioning section of the P&B valve proportions outlet pressure to the rear brakes after a predetermined rear input pressure has been reached.
This is done to prevent rear wheel lock up on the vehicles with light rear wheel loads. The valve has a pass feature which assures full system pressure to
the rear brakes in the event of front brake system malfunction. Also full front pressure is retained in the event of rear brake malfunction.
The combination valve has a pressure differential warning switch which is designed to constantly compare front and rear brake pressure from the master
cylinder and turn on the brake system warning light on the instrument panel in the event of a front or rear system malfunction. The valve and switch are
so designed that the switch will latch in the warning position once a malfunction has occurred. The only way the light can be turned off is to repair the
malfunction and apply a pedal forced required to developed line pressure. The P&B valve is not repairable and must be replaced as a complete assembly.
