FixVault

Fail-Safe Chart

WARNING: This page is about a different variant/trim than selected.
Fig 1: Hydraulic Pressure System Diagram
G05641910Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  1. FAIL-SAFE FUNCTION 
    1. If a malfunction occurs in the skid control ECU, sensor signal, or actuator, the remaining functioning components will maintain brake control.
    2. When trouble occurs in the brake control system, the skid control ECU turns the warning light on, and prohibits ABS, BA, and VSC operations.

      ABS, EBD and BA system: 

      ABS, EBD AND BA SYSTEM AND FAIL-SAFE FUNCTION CHART

      Malfunctioning Area Control Method
      ABS system ABS, BA, TRAC and VSC control prohibited
      BA system ABS, BA, TRAC and VSC control prohibited
      EBD system ABS, EBD, BA, TRAC and VSC control prohibited

      HINT:

      A malfunction in either the ABS or BA system will result in an identical operation, with the ABS, BA, TRAC and VSC system control disabled.

      TRAC and VSC system: 

      TRAC AND VSC SYSTEM AND FAIL-SAFE FUNCTION CHART

      Malfunctioning Area Control Method
      Hybrid control system (TRAC and VSC systems) Before control: Disables control
      During control: Uses only the brakes to effect control
      Brake control system (TRAC and VSC systems) Before control: Disables control
      During control: Disables control (by gradually ending control)

      HINT:

      As for the TRAC and VSC systems, different systems prohibit different controls depending on the malfunctioning part.

    3. The skid control ECU prevents operation of a malfunctioning hydraulic system and continues brake control with a backup hydraulic system.

      HINT:

      • If control of the electronically controlled brake system is prohibited for any of the wheels, that wheel loses brake accumulator function or braking ability.
      • If one of the wheels loses brake accumulator function, the feeling when depressing the brake pedal changes as the stroke simulator (pedal reactive force generating solenoid) operation will be prohibited.
      • If control of the electronically controlled brake system is prohibited for all wheels, the 2 front wheels will lose brake accumulator function.
    4. If the brake control is stopped under such conditions as when trouble occurs with a hydraulic pressure source, the pressure generated in the master cylinder by the driver is applied to the front wheel cylinders to ensure braking force.
    5. A power back-up unit is built in as an additional power source to supply stable power to the system.
    6. If the regenerative brake alone does not operate under such conditions as a communication error with the hybrid vehicle control ECU, control is switched so that all braking force is generated with hydraulic braking pressure.
    MALFUNCTIONING AREA AND GENERATED BRAKING FORCE

    Malfunctioning Area Generated Braking Force
    Skid control ECU Normally operating parts will control brake and generated braking force
    Hydraulic pressure controlling parts Normally operating parts will control brake and generated braking force
    Hydraulic pressure source Braking force generated by the driver