Hydraulic Control Assembly - Antilock Brakes: Description and Operation

Hydraulic control module




The hydraulic control module is located under the bonnet adjacent to the engine compartment bulkhead. It is secured within a steel mounting bracket at three securing points.

The hydraulic pump (1) is a reciprocating two circuit pump in which one brake circuit is assigned to each pump circuit. The pump supplies adequate pressure and volume supply to the brake circuits under anti-lock braking conditions. The pump housing incorporates a low pressure accumulator and damping chamber for each brake circuit. The pump is driven by an electric motor (2) which draws 32A current at peak operation and has an internal resistance of 0.8 ohm.

The modulator valve block (3) houses six solenoid valves: three normally open (NO) inlet valves and three normally closed (NC) outlet valves. This provides three outlet ports, one for each front brake and one for both rear brakes.

All electronic and power connections are made through one cable loom connector to the ABS control module (4) located below the valve block.

The pump, motor and valve block are nonserviceable. If a fault occurs in any of these components, the whole hydraulic control module must be replaced. The ABS CM control module can be replaced separately.