System Outline

System Outline

ABS Operation
This system controls the respective brake fluid pressures acting on the disc brake cylinders of the right front wheel, left front wheel, and rear wheels when the brakes are applied in a panic stop so that the wheels do not lock.
This results in improved directional stability and steerability during panic braking.

1. Input Signal
1. Speed sensor signal
The speed of the wheels is detected and input to TERMINALS FL+, FR+, RL+ and RR+ of the skid control ECU with actuator.
2. Stop light SW signal
A signal is input to TERMINAL STP of the skid control ECU with actuator when the brake pedal is depressed.

2. System Operation
During sudden braking, the skid control ECU with actuator which has signals input from each sensor lets the hydraulic pressure acting on each wheel cylinder escape to the reservoir.
The pump inside the skid control ECU with actuator is also operating at this time and it returns the brake fluid from the reservoir to the master cylinder, thus preventing locking of vehicle wheels.
If the skid control ECU with actuator judges that the hydraulic pressure acting on the wheel cylinder is insufficient, the current acting on the solenoid is controlled and the hydraulic pressure is increased.
Holding of the hydraulic pressure is also controlled by the ECU, by the same method as above, by repeated pressure reduction. Holding and increase are repeated to maintain vehicle stability and to improve steerability during sudden braking.

VSC Operation
The vehicle could be in an extreme oversteering or understeering tendency due to unexpected accidents, road conditions, vehicle speed, or by other external factors. In such a case, this system automatically controls the engine output and the braking to each wheel, to decrease the extreme oversteering and understeering.
- To decrease extreme oversteering tendency
When the system determines that the oversteering tendency is large, the system applies brakes to the outer wheels according to the degree of oversteering, and creates a moment towards the outer side of the vehicle, to decrease the tendency of oversteering. Also, when the brakes are applied, the vehicle speed decreases while the stability increases.
- To decrease extreme understeering tendency
When the system determines that the understeering tendency is large, the system applies brakes to the front or rear wheels according to the degree of understeering, to decrease the tendency of understeering.
When the VSC operated, the skid control ECU with actuator sends a signal and the slip indicator in the instrumental cluster will flash and a buzzer will sound to warn the driver than the tire grip is at its limit.

Active Traction Control (4WD)
While driving with the 4WD mode, the active TRAC system helps control the spinning of the wheels which may occur when accelerating on a snowy road or during severe off-road driving, by controlling the brake fluid pressure of each wheel. The system distributes the traction lost by slipping to each wheel, which produces a strong LSD effect. When the active TRAC is in use, the skid control ECU with actuator sends a signal and the slip indicator in the instrumental cluster will flash and a buzzer will sound to notify the driver.

Traction Control Operation (2WD)
Estimating the vehicle speed from the rear wheel speed, comparing it with the front, driving wheel speed and judging the grip condition of the driving wheels. From the estimated vehicle speed, target speed of the driving speed will be set. When the front, driving wheel speed exceeds the control starting speed, it judges that the tire slip is occurred and performs the fuel cut cylinder number control and brake control and then adjust to make the front wheel speed become the traction control target speed. Controlling of the traction control will be completed when the vehicle move on to the road where the driving wheels will not have a tire slip or when the driver decelerate.