Vehicle Stability Control System (For Hydraulic Brake Booster) -- System Description |
SYSTEM DESCRIPTION |
- HINT:
- The skid control ECU (master cylinder solenoid) is built into the hydraulic brake booster.
ABS (Anti-lock Brake System)
The ABS helps prevent the wheels from locking when the brakes are applied firmly or on a slippery surface.Multi-terrain Anti-lock Brake System (Multi-terrain ABS)
The multi-terrain ABS operates in conjunction with multi-terrain select control. This function detects off-road driving in sand, mud, gravel, dirt and so on based on signals from the yaw rate and acceleration sensor, the speed sensor and the ECM, and then automatically switches to the ABS control most appropriate for the current road conditions.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.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.TRC (Traction Control)
The TRC 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.VSC (Vehicle Stability Control)
The VSC system helps prevent the vehicle from slipping sideways when front or rear wheel skidding occurs while cornering.A-TRC (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.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.
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.
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.Multi-terrain Select Control
When multi-terrain select control is active, A-TRC 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.Trailer Sway Control
If the vehicle is towing a trailer with an inappropriate hitch load, trailer sway could be caused by crosswinds, imbalance caused by load, or the driver's steering. Trailer sway control reduces trailer sway by controlling the engine output and the braking of each wheel.
FUNCTION OF COMPONENTS |
Components | Functions | |
Hydraulic brake booster assembly | Upon receiving a brake control signal from the skid control ECU (master cylinder solenoid), the hydraulic brake booster controls the hydraulic circuit and sends hydraulic pressure to each wheel. The skid control ECU (master cylinder solenoid) is removable. | |
Hydraulic brake booster assembly | Skid control ECU (Master cylinder solenoid) | Detects the vehicle condition based on signals from the sensors and sends a brake control signal to the hydraulic brake booster. |
Motor relay | Supplies a power source to the pump motor. | |
Solenoid relay | Supplies a power source to each solenoid. | |
Master cylinder pressure sensor | Built into the master cylinder solenoid. Detects the pressure inside the master cylinder. | |
Accumulator pressure sensor | Built into the master cylinder solenoid and detects the accumulator pressure. | |
Speed sensor | Detects the wheel speed of each wheel. | |
Steering angle sensor (Spiral cable sub-assembly) | Detects the steering angle and amount of movement of the steering wheel, and then sends signals to the skid control ECU (master cylinder solenoid). | |
Yaw rate and acceleration sensor (Yaw rate sensor assembly) | Detects the vehicle's yaw rate and acceleration and sends a signal to the skid control ECU (master cylinder solenoid). | |
ECM |
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VSC OFF switch | Enables the driver to select Normal Mode, TRC OFF Mode or VSC OFF Mode. | |
Downhill assist control switch*1 | Allows the driver to turn downhill assist control on and off. | |
Center cluster module switch | Crawl on/off switch *2 | Turns the crawl on and off. |
Crawl speed selector*2 | Used to select the target vehicle speed when the crawl is active. | |
Multi-terrain select switch*2 | Turns the multi-terrain select on and off. | |
Multi-terrain select road mode selector*2 | Selects multi-terrain select road mode. | |
Combination meter assembly | ABS warning light |
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Brake warning light |
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TRC OFF indicator light | Illuminates to inform the driver when the vehicle is in TRC OFF mode. | |
VSC OFF indicator light | Illuminates to inform the driver that VSC OFF mode is entered using the VSC OFF switch. | |
Slip indicator light |
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Downhill assist control indicator light*1 | Illuminates to inform the driver when downhill assist control operation is possible. | |
Multi-terrain select indicator light*2 | Illuminates to inform the driver that multi-terrain select control is ready to operate. | |
Multi-information display*3 |
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Buzzer | Sounds to warn the driver that a malfunction in the hydraulic brake booster assembly has occurred. The buzzer also sounds when hill-start assist control operates or crawl control is canceled. | |
Skid control buzzer assembly*4 | Sounds after the skid control ECU (master cylinder solenoid) receives the buzzer signal from the driving support ECU. |
- *1: w/ Downhill Assist Control
- *2: w/ Crawl Control
- *3: w/ Multi-information Display
- *4: w/ Dynamic Radar Cruise Control System