System Description

HINT:

The skid control ECU is built into the VSC actuator.

1. ABS (Anti-lock Brake System)

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

   Fig 1: Anti-Lock Brake System Communication Diagram

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Operation description

      The skid control ECU detects wheel lock conditions by receiving vehicle speed signals from each speed sensor, and sends control signals to the pump motor and solenoid valve to prevent the wheels from locking by controlling the brake fluid pressure of each wheel cylinder. The ABS warning light comes on when the ABS system malfunctions.

2. EBD (Electronic Brake Force Distribution)

   The EBD control utilizes the ABS, performing 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 rear right and rear left wheels, helping to maintain vehicle stability.

   Fig 2: Electronic Brake Force Distribution Communication Diagram

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Operation description

      The skid control ECU receives speed signals from each speed sensor to detect the slip conditions of the wheels and sends control signals to the solenoid.

      The solenoid valve controls the brake fluid pressure of each wheel cylinder, and divides the control power properly between the front and rear wheels and the rear right and rear left wheels.

      The BRAKE warning light comes on to indicate malfunctions in the EBD system.

3. 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.

   Fig 3: Brake Assist Communication Diagram

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Operation description

      The skid control ECU receives speed signals from each speed sensor and the fluid pressure signal from the master cylinder pressure sensor to determine whether brake assist is necessary. If brake assist is deemed necessary, the skid control ECU sends control signals to the pump motor and solenoid. The pump and the solenoid valve then control the pressure applied to each wheel cylinder. The ABS warning light comes on to indicate malfunctions in the BA system.

4. Changing of TRAC, AUTO LSD and VSC operation permission/disablement through VSC OFF switch
   1. Changing modes:

      Through the VSC OFF switch, the vehicle can be changed to normal mode, TRAC OFF mode, AUTO LSD mode and VSC OFF mode.

      Fig 4: Identifying VSC OFF Switch

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002