System Outline

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 ABS ECU.

2. Stop Light SW Signal
A signal is input to TERMINAL STP of the ABS ECU when the brake pedal is depressed.

3. Parking Brake SW Signal
A signal is input to TERMINAL PKB of the ABS ECU when the parking brake SW is ON.

4. Deceleration Sensor Signal
The degree of vehicle deceleration is detected and input to TERMINAL GS1, GS2 and GST of the ABS ECU.

5. Transfer Control Signal
While the transfer shift lever is in L4 position, the center diff. lock indicator SW detects a signal of the center diff. lock and the signal is input to TERMINAL EXI of the ABS ECU.

2. SYSTEM OPERATION
(Transfer L4 Position)
When the transfer shift lever is moved to L4 position, the center diff. is locked, then the ABS is not in operation and the ABS warning light is lighted up.

(Transfer Except L4 Position)
During sudden braking, the ABS ECU which has signals input from each sensor, controls the current to the solenoid inside the actuator, and causes 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, 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 increased are repeated to maintain vehicle stability and improve steerability during sudden braking.