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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 209 (Anti-Lock Brake System - Hybrid) >> Description & Operation >> ABS Description & Operation >> Slip Control Boost (SCB) Overview >> Base Brake Valves (Normal Closed)

Base Brake Valves (Normal Closed)

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

The normally closed base brake valve (N/C valve) is used to close off a passage which allows fluid from the back side (spring side) of the simulator and from the tank port of the boost valve to exit to the reservoir. In normal braking, turning this valve on (opening) allows the simulator to compress the spring and function normally. During failed system operation (push-through) the valve is left off (closed) keeping fluid from exiting the back side of the simulator, which in turn keeps MC fluid from entering the front side of the simulator. In this way, fluid from the MC during failed system, and push through operation is applied only to the wheel brakes, and not lost in the simulator. In normal operation the valve is turned on (opened).