Antilock Brakes / Traction Control Systems: Description and Operation
BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: VEHICLE STABILITY CONTROL SYSTEM: SYSTEM DIAGRAM
BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: VEHICLE STABILITY CONTROL SYSTEM: SYSTEM DESCRIPTION
1. SYSTEM DESCRIPTION
HINT
The skid control ECU is built into 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 on a slippery surface.
(b) Multi-terrain Anti-lock Brake System (Multi-terrain ABS)
The multi-terrain ABS operates in conjunction with the multi-terrain select. This function detects off-road driving in sand, mud, gravel, dirt and so on based on signals from the yaw rate and acceleration sensor, speed sensor and ECM, and then automatically switches to the ABS control most appropriate for the road condition.
(c) EBD (Electronic Brake Force Distribution)
EBD control utilizes the ABS and performs proper brake force distribution between the front and rear wheels in accordance with the driving conditions. When the brakes are applied while cornering, it also controls the braking forces of the right and left wheels, helping to maintain vehicle stability.
(d) BA (Brake Assist)
The primary purpose of the brake assist system is to provide auxiliary brake force to assist drivers who cannot generate a brake force large enough during emergency braking, thus helping to maximize the vehicle's braking performance.
(e) TRAC (Traction Control)
The TRAC system helps prevent the drive wheels from slipping if the driver depresses the accelerator pedal excessively when starting off or accelerating on a slippery surface.
(f) VSC (Vehicle Stability Control)
The VSC system helps prevent the vehicle from slipping sideways when front or rear wheel skidding occurs while cornering.
(g) A-TRAC (Active Traction Control)
During rugged off-road driving, this system controls the engine output and the brake fluid pressure that is applied to the slipping wheel 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.
(h) AUTO LSD (Auto Limited Slip Differential)
The AUTO LSD operates with the VSC OFF switch on and the accelerator pedal depressed.
The AUTO LSD system is used to restrain brake pressure and reduce differential movement, thus transmitting drive torque to the other drive wheel to ensure startability under the following conditions:
* Wheels run off the road.
* Drive wheels slip when starting on a slope with one wheel on snow/ice.
(i) Downhill Assist Control
When the downhill assist control switch is pressed with the transfer in the low (L4) range and without the accelerator and brake pedals in operation, 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. Therefore, 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.
(j) 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 performs 4-wheel hydraulic pressure control to reduce the speed of the vehicle.
HINT
* Depressing the brake pedal cancels control of the hill-start assist control system.
* The system does not operate when the shift lever is in P or N, or when the vehicle is running/rolling back up a slope with the shift lever in R.
(k) Crawl (Crawl Control)
Crawl control is a system that provides assistance when driving on bumpy off-road surfaces, slippery road surfaces, etc. When crawl control is operating, the engine output and braking force are controlled automatically to enable driving while maintaining a constant speed. As a result, the driver can concentrate on steering the vehicle without having to operate the accelerator and brake pedals very much.
(l) Multi-terrain Select Control
When multi-terrain select control is active, A-TRAC brake control and engine output control most appropriate for the selected road mode are performed automatically. In this way, superior off-road driveability is achieved.
2. FUNCTION OF COMPONENTS
*1: for 4WD
*2: w/ Downhill Assist Control
*3: w/ Crawl Control
*4: for 2WD