Anti-lock Braking System
For AWD models, a two-phase ABS is required (a three-phase system would result in severe vibration and stress in the drivetrain). While the speed of all four wheels is monitored independently, braking action occurs for at least two wheels simultaneously. This is a fail-safe system; the three stage hydraulic valving defaults to normal non-ABS braking even when the ABS system is malfunctioning.
The system consists of wheel speed sensors, proportioning valves (left-right and front-back), hydraulic unit and the electronic control unit.