Acura TSX / Honda Accord CL. Manual — part 275

Fig. 13: VSA Understeer Control (In Acceleration)

MODULATOR UNIT

The modulator 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.

2004 Acura TSX

2004 BRAKES Vehicle Stability Assist System - TSX

Fig. 14: ABS Control Pump Motor Schematic

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.

Fig. 15: ABS Control Pressure Retaining Mode Schematic

Pressure Reducing Mode

2004 Acura TSX

2004 BRAKES Vehicle Stability Assist System - TSX

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

Fig. 16: ABS Control Pressure Reducing Mode Schematic

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.

2004 Acura TSX

2004 BRAKES Vehicle Stability Assist System - TSX

Fig. 17: TCS Control Pressure Intensifying Mode Schematic

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.

Fig. 18: TCS Control Pressure Retaining Mode Schematic

Pressure Reducing Mode

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

2004 Acura TSX

2004 BRAKES Vehicle Stability Assist System - TSX