VSA System Description

VSA Modulator-Control Unit Inputs and Outputs for 37P Connector

 

Terminal number Wire color Terminal sign Description Measurement (Disconnect the VSA modulator-control unit 37P connector) 
Terminals Conditions Voltage 
1 RED CAN-L F-CAN communication circuit ——— ——— ——— 
3 BLU STR-D Detects steering angle sensor signal 
6 PNK FR-GND Detects right-front wheel sensor signal 
7 ORN SVCC Power source for the steering angle sensor 
8 PUR RL-GND Detects left-rear wheel sensor signal 
9 LT GRN RR +B Detects right-rear wheel sensor signal 
10 BRN SGND Ground for the steering angle sensor 
11 GRY*1
RED*2 		FL-GND Detects left-front wheel sensor signal 
13 WHT FSR +B Power source for the fail-safe relay 13-GND At all times Battery voltage 
14 RED MR +B Power source for the motor relay 14-GND At all times Battery voltage 

*1: Except K20Z2 engine model 
*2: K20Z2 engine model 
*3: LHD type 
*4: RHD type 

Terminal number Wire color Terminal sign Description Measurement (Disconnect the VSA modulator-control unit 37P connector) 
Terminals Conditions Voltage 
15 WHT CAN-H F-CAN communication circuit ——— ——— ——— 
17 PUR STR-B Detects steering angle sensor signal 
19 GRN FR +B Detects right-front wheel sensor signal 
20 BLU*1
YEL*2 		RL +B Detects left-rear wheel sensor signal 
21 WHT*1
BLU*2 		RR-GND Detects right-rear wheel sensor signal 
22 ORN*1
WHT*2 		FL +B Detects left-front wheel sensor signal 
26 LT BLU K-LINE Communications with HDS 
   28*3 GRY*1
YEL*2 		IG1 Power source for activating the system 28-GND Ignition switch ON (II) Battery voltage 
   28*4 GRY 
34 GRN STR-A Detects steering angle sensor signal ——— ——— ——— 
36 BLK GND Ground for the VSA modulator-control unit 36-GND At all times 0.1 V or less 
37 BLK MR-GND Ground for the pump motor 37-GND At all times 0.1 V or less 

*1: Except K20Z2 engine model 
*2: K20Z2 engine model 
*3: LHD type 
*4: RHD type 

System Outline


This system is composed of the VSA modulator-control unit, the wheel sensor, steering angle sensor, and yaw rate-lateral acceleration sensor and system indicators in the gauge control module. The VSA modulator-control unit controls the ABS, EBD, TCS, and brake assist with the brake pressure of each wheel and the engine torque.

 

ABS Features


Anti-lock control

Without ABS, when the brake pedal is pressed while driving, the wheels sometimes lock before the vehicle comes to a stop. In such an event, the maneuverability of the vehicle is reduced if the front wheels are locked, and the stability of the vehicle is reduced if the rear wheels are locked, creating an extremely unstable condition. With ABS, the system precisely controls the slip rate of the wheels to ensure maximum grip force from the tyres, and it thereby ensures maneuverability and stability of the vehicle. The ABS calculates the slip rate of the wheels based on the four wheel speed, then it controls the brake fluid pressure to reach the target slip rate.

Grip force of tyre and road surface 


Main Control

The control unit detects the wheel speed based on the wheel sensor signals it received, then it calculates the vehicle speed based on the detected wheel speed. The control unit detects the vehicle speed during deceleration based on the rate of deceleration.

The control unit calculates the slip rate of each wheel, and transmits the control signal to the modulator unit solenoid valve when the slip rate is high.

The hydraulic control has three modes: Pressure intensifying, pressure reducing and, pressure retaining.

 

EBD Features


The electronic brake distribution (EBD) helps control vehicle braking by adjusting the rear brake force in accordance with rear wheel load before the ABS operates. Based on wheel sensor signals, the control unit uses the modulator to control the rear brakes individually. When the rear wheel speed is less than the front wheel speed, the VSA modulator-control unit retains the current rear brake fluid pressure by closing the inlet valve in the modulator. As the rear wheel speed increases and approaches the front wheel speed, the VSA modulator-control unit increases the rear brake fluid pressure by momentarily opening the inlet valve. This whole process is repeated very rapidly. While this is happening, there is kickback at the brake pedal.

 


TCS Features


When a drive wheel loses traction on a slippery road surface and starts to spin, the VSA modulator-control unit applies brake pressure to the spinning wheel and sends engine torque control request to the PCM to slow the spinning wheel and keep traction.

 

VSA System Features


Oversteer control

Applies the brake to the front and rear outside wheels

 

Understeer control

 

Brake Assist Features


Brake assist helps ensure that any driver can achieve the full braking potential of the vehicle by increasing brake system pressure in a panic situation, bringing the vehicle into a full ABS stop.
Each time the ignition switch is turned ON (II), the VSA modulator-control unit learns the current driver's normal braking characteristics by monitoring the brake pressure sensor and the brake pedal position switch at each stop. Using these inputs and their values, the VSA modulator-control unit is able to learn the driver's normal braking habits, and then determine the difference between a normal stop and a panic stop for the individual driver of the vehicle. If during a panic stop the VSA modulator-control unit determines that the brake system pressure increases above a learned threshold in less than a learned amount of time, the VSA modulator-control unit engages brake assist.
Because the brake system pressure crossed the threshold before the time threshold had expired, the VSA modulator-control unit goes into brake assist mode.

 

Modulator Unit


The modulator unit consists of the inlet solenoid valve, outlet solenoid valve, VSA NO (normally open) solenoid valve, VSA NC (normally closed) solenoid valve, reservoir, pump, pump motor, and the damping chamber.
The hydraulic control has three modes at ABS action; pressure intensifying, pressure retaining, and pressure reducing. And pressure adding mode is combined at TCS, VSA, and brake assist action.
The hydraulic circuit is an independent four channel type, one channel for each wheel.

 

Mode VSA NO Valve VSA NC Valve Inlet Solenoid Valve Outlet Solenoid Valve Brake Fluid 
Pressure intensifying mode open closed open closed Master cylinder fluid is pumped out to the caliper. 
Pressure retaining mode open closed closed closed Caliper fluid is retained by the inlet valve and outlet valve. 
Pressure reducing mode open closed closed open 
  • Caliper fluid flows through the outlet valve to the reservoir.
  • The reservoir fluid is pumped out by the pump with motor*, through the damping chamber, to the master cylinder.
 
Pressure adding mode closed open open closed 
  • Master cylinder fluid is pumped out by pump with motor through VSA NC valve to the caliper.
  • Caliper fluid pressure exceed master cylinder pressure.
 

*: The motor will be keep the action until operation of the one anti-lock brake control is finished from the first pressure reducing mode.