System Outline

ABS system controls the respective brake fluid pressures acting on the disc brake cylinders of the four 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.

Tire pressure warning system turns on the tire pressure warning light and warns the driver of low tire pressure, when driving with a low tire pressure, which may cause trouble driving.

However, this system can detect the low tire pressure condition only if one of the tires has such a condition in particular compared to other tires, and it cannot detect. Therefore, it can not detect natural (Gradual) air loss occurring to the tires.

1. Input Signals 
   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 operated.

   3. Parking position signal

      A signal is input to TERMINAL P of the skid control ECU with actuator when the Shift lever at "P" position.

   4. Neutral position signal

      A signal is input to TERMINAL N of the skid control ECU with actuator when the Shift lever at "N" position.

2. ABS System Operation 

   During sudden braking the skid control ECU with actuator has signals input from each sensor, which controls the current to the solenoid inside the actuator and lets the hydraulic pressure acting on each wheel cylinder escape to the reservoir. The pump inside the actuator is also operating at this time, and it returns the brake fluid from the reservoir to the master cylinder, thus preventing locking of the vehicle wheels.

   If the skid control ECU with actuator judges that the hydraulic pressure acting on the wheel cylinder is insufficient, the current on the solenoid is controlled and the hydraulic pressure is increased. Holding of the hydraulic pressure is also controlled by the skid control ECU with actuator, by the same method as above. Pressure reduction, holding and increase are repeated to maintain vehicle stability and to improve steerability during sudden braking.