Antilock Brakes / Traction Control Systems: Description and Operation

This system controls the respective brake fluid pressures acting on the brake cylinders of the right front wheel, the left front wheel and the 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 SIGNALS
1. Speed sensor signal
The speed of the wheels is detected and input to TERMINALS FL+, FR+ RL+ and RR+ of the ABS ECU.
2. Stop light SW signal
A signal is input to TERMINAL STP of the ABS ECU when the brake pedal depressed.

2. SYSTEM OPERATION
During sudden braking the ABS ECU which has signals input from each of the sensor, controls current to the solenoid inside the actuator and causes the hydraulic pressure acting on each of the 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, preventing locking of the vehicle wheels.
If the ECU 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.