System Description

BRAKE CONTROL: VEHICLE STABILITY CONTROL SYSTEM (for Hydraulic Brake Booster): SYSTEM DESCRIPTION

1. SYSTEM DESCRIPTION

HINT
* The skid control ECU (master cylinder solenoid) forms a single unit with the hydraulic brake booster.
* The yaw rate sensor and deceleration sensor are combined in a single unit. This unit communicates with the skid control ECU (master cylinder solenoid) through CAN communication.

(a) ABS (Anti-lock Brake System)

The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface.

(b) EBD (Electronic Brake force Distribution)

The EBD control utilizes ABS, realizing proper brake force distribution between the front and rear wheels in accordance with the driving conditions.

In addition, when braking while cornering, it also controls the brake forces of the right and left wheels, helping to maintain the vehicle stability.

(c) VSC (Vehicle Stability Control)

The VSC system helps prevent the vehicle from slipping sideways as a result of strong front wheel skid or strong rear wheel skid during cornering.

(d) TRAC (Traction Control)

The TRAC system helps prevent the drive wheels from slipping if the driver presses down on the accelerator pedal excessively when starting off or accelerating on a slippery surface.

HINT
The TRAC system operates when H2 (2WD) mode is selected.

(e) A-TRAC (Active Traction Control)

During rugged off-road driving, this function controls the brake fluid pressure that is applied to slipping wheels, and distributes the drive force that would have been lost through the slippage to the remaining wheels in order to achieve an LSD (Limited Slip Differential) effect. As a result, the vehicle's off-road driveability and ability to free itself from ruts have been increased.

HINT
The A-TRAC system operates when L4 (Low speed 4WD) mode is selected.

(f) AUTO-LSD (Auto Limited Slip Differential)

When the vehicle is in H2 (2WD) mode, the AUTO LSD will operate with the VSC OFF switch on (TRAC OFF mode (AUTO LSD control)) and the accelerator pedal depressed.

the AUTO LSD will operate with the VSC OFF switch on (TRAC OFF mode (AUTO LSD control)) and the accelerator pedal depressed. The AUTO LSD system is used to apply brake pressure and limit differential slippage, thus transmitting drive torque to the other drive wheel to ensure traction when starting under the following conditions:

* One of the drive wheels spins, for example, when one drive wheel is driven off of the pavement.

* One of the drive wheels slips on snow/ice when starting on a slope.

HINT
The AUTO LSD system operates when H2 (2WD) mode is selected.

(g) Downhill Assist Control

When the downhill assist control switch is pressed with the transfer in low (L4) range and without the accelerator and brake pedals in operation, the downhill assist control activates 4-wheel hydraulic pressure control, in order to maintain a constant low vehicle speed without causing the wheels to become locked. Thus, the vehicle can descend steep hills in a stable manner.

HINT
Depressing the accelerator and brake pedals cancels control of the downhill assist control system.

Begins operating when driving down slopes at a speed of 25 km/h (16 mph) or less with the engine brake applied.

(h) Hill-start Assist Control

When the vehicle starts off on a steep hill, hill-start assist control detects the backward descent of the vehicle and effects 4-wheel hydraulic pressure control to reduce the speed of the vehicle.

For a Maximum of 5 seconds after the control starts, fluid pressure is gradually released and the control is complete.

HINT
Depressing the brake pedal cancels control of the hill-start assist control system.

Does not operate when the shift lever in P or N, or when the vehicle is running/rolling back up a slope with the shift lever in R.

2. ABS with EBD and BA and TRAC and VSC operation

(a) The skid control ECU (master cylinder solenoid) determines the wheel slipping conditions by receiving signals from each speed sensor, the yaw rate and deceleration sensor, and the steering angle sensor. The ECU controls the engine output torque using electronic throttle control, and the wheel brake pressure using the master cylinder solenoid, according to these signals.

The slip indicator blinks and the VSC warning buzzer sounds to inform the driver that the VSC system is operating. The slip indicator also blinks when TRAC is operating, and the operation being performed is displayed.

3. INITIAL CHECK

(a) When the vehicle speed first reaches approximately 6 km/h (4 mph) or more after the ignition switch has been turned ON, each solenoid valve and the brake actuator motor are sequentially activated to perform electrical checks. During the initial check, the operating sound of the motor can be heard from the engine compartment, but this does not indicate a malfunction.

4. FUNCTION OF COMPONENTS