Vehicle Stability Control System

BRAKE CONTROL: VEHICLE STABILITY CONTROL SYSTEM: SYSTEM DIAGRAM






















SYSTEM DESCRIPTION

1. SYSTEM DESCRIPTION

HINT
The skid control ECU forms a single unit with the hydraulic brake booster.

(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 and vehicle load.

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

(c) BA (Brake Assist)

The primary purpose of the brake assist system is to provide an auxiliary brake force to assist drivers who cannot generate a large enough brake force during emergency braking, thus helping to maximize the vehicle's brake performance.

(d) 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.

(e) 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 or accelerating on a slippery surface.

(f) A-TRAC (Active Traction Control)

During rugged off-road driving, this function controls the engine output and 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 drivability and ability to free itself from bumps have been increased.

HINT
The A-TRAC system operates when 4WD mode is selected (4WD vehicles only).

(g) AUTO-LSD (Auto Limited Slip Differential) (2WD Vehicles Only)

The AUTO LSD operates with the VSC OFF switch on and the accelerator pedal depressed.

The TRAC system restrains brake pressure and reduces differential movement, thus transmitting the drive torque to the other drive wheel to ensure stability under the following conditions:

* Wheels run off the road.

* Drive wheels run idle when starting on a slope with one wheel on snow/ice.

HINT
Depressing the brake pedal cancels control of the AUTO LSD system.

2. ABS with EBD, BA, TRAC, AUTO LSD, A-TRAC and VSC OPERATION

(a) The skid control ECU calculates vehicle stability tendency based on the signals from the 4 wheel speed sensors, the yaw rate and deceleration sensor, and the steering angle sensor. In addition, it evaluates the results of the calculations to determine whether any control actions (control of the engine output torque by electronic throttle control and of the brake fluid pressure by the hydraulic brake booster) should be implemented.

3. INITIAL CHECK

(a) When the vehicle speed first reaches approximately 6 km/h (4 mph) or more after the ignition switch is turned ON, each solenoid valve and the motor of the hydraulic brake booster 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





*1: w/ A-TRAC

*2: 2WD