Normal Operation
WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The ABS module internally monitors the HCU internal pressure and the hydraulic brake pressure to each wheel. If the pressure drops below acceptable limits, the ABS module sets a DTC and the red brake warning indicator and ABS light illuminate.