VSA - Components
Components
The VSA system consists of the following primary components:
- VSA modulator-control unit
- Wheel speed sensors
- Magnetic encoders
- VSA OFF switch
- System indicator
For locations of each component on vehicle, refer to Component Location Index , and for functions of indicator, refer to How to Troubleshoot the VSA System .
VSA Modulator
The VSA modulator unit consists of the inlet solenoid valve, the outlet solenoid valve, the VSA NO (normally open) solenoid valve, the VSA NC (normally closed) solenoid valve, the reservoir, the pump, and the pump motor. The hydraulic control has four modes; pressure intensifying, pressure retaining, pressure reducing, and pressure intensifying mode.
| Mode | VSA NO Solenoid Valve | VSA NC Solenoid Valve | Inlet Solenoid Valve | Outlet Solenoid Valve | Brake Fluid |
|---|---|---|---|---|---|
| Pressure intensifying mode | open | closed | open | closed | Tandem motor cylinder fluid is pumped out to the caliper. |
| Mode | VSA NO Solenoid Valve | VSA NC Solenoid Valve | Inlet Solenoid Valve | Outlet Solenoid Valve | Brake Fluid |
|---|---|---|---|---|---|
| Pressure retaining mode | open | closed | closed | closed | Caliper fluid is retained by the inlet and outlet solenoid valves. |
| Pressure reducing mode | open | closed | closed | open | Caliper fluid flows through the outlet solenoid valve to the reservoir. |
| Pressure intensifying mode (VSA) | closed (current control) | open | open | closed |
|
Wheel Speed Sensor
The VSA system uses 4 wheel speed sensors to monitor individual wheel speed. The wheel speed sensor is a semiconductor, Hall effect sensor, and detects the magnetic field of a magnetic encoder installed on the inner sealing surface of each hub and wheel bearing assembly. The frequency of the sensor output signal is proportional to the speed of the wheel and this signal information is sent to the VSA control unit.