Electronic Brake Control Module: Description and Operation

VSA Modulator-Control Unit
The VSA modulator-control unit consists of the inlet solenoid valve, outlet solenoid valve, VSA normally open (NO) solenoid valve, VSA normally closed (NC) solenoid valve, reservoir, pump, pump motor, and the damping chamber. The modulator controls the caliper fluid pressure directly. It is a circulating-type modulator because the brake fluid circulates through the caliper, the reservoir, and the master cylinder. The hydraulic control has three modes: pressure intensifying, pressure retaining, and pressure reducing. The hydraulic circuit is an independent four channel type, one channel for each wheel.

ABS Control
Pressure intensifying mode
VSA NO valve open, VSA NC valve closed, inlet valve open, outlet valve closed. Master cylinder fluid is pumped out to the caliper.

Pump Motor





When starting the pressure reducing mode, the pump motor is ON. When stopping ABS operation, the pump motor is OFF.
The reservoir fluid is pumped out by the pump, through the damping chamber, to the master cylinder.

Pressure retaining mode





VSA NO valve open, VSA NC valve closed, inlet valve closed, outlet valve closed. Caliper fluid is retained by the inlet valve and outlet valve.

Pressure reducing mode





VSA NO valve open, VSA NC valve closed, inlet valve closed, outlet valve open. Caliper fluid flows through the outlet valve to the reservoir.

TCS Control
Pressure intensifying mode





VSA NO valve closed, VSA NC valve open, inlet valve open, outlet valve closed, pump motor ON. The reservoir and master cylinder fluid is pumped out by the pump, through the damping chamber, to the front caliper.

Pressure retaining mode





VSA NO valve closed, VSA NC valve open, inlet valve closed, outlet valve closed, pump motor ON. Front caliper fluid is retained by the inlet valve and outlet valve.

Pressure reducing mode





VSA NO valve closed, VSA NC valve open, inlet valve closed, outlet valve open, pump motor ON. Caliper fluid flows through the outlet valve to the reservoir.

VSA Control
Pressure intensifying mode





VSA NO valve closed, VSA NC valve open, inlet valve open, outlet valve closed, pump motor ON. The reservoir and master cylinder fluid is pumped out by the pump, through the damping chamber, to the front and rear calipers.

Pressure retaining mode





VSA NO valve closed, VSA NC valve open, inlet valve closed, outlet valve closed, pump motor ON. Front and rear caliper fluid is retained by the inlet valve and outlet valve.

Pressure reducing mode





VSA NO valve closed, VSA NC valve open, inlet valve closed, outlet valve open, pump motor ON. Caliper fluid flows through the outlet valve to the reservoir.