2012 Toyota Prius FiveFACTORY OEM SERVICE PROCEDURE

Fail-Safe Chart

  1. FAIL-SAFE FUNCTION OF CONTROL SYSTEM 
    1. When a malfunction is detected in the brake control system, the skid control ECU turns the ABS warning, brake warning / red (malfunction), brake warning / yellow (minor malfunction) and slip indicator lights come on, as well as prohibits ABS, BA, TRAC and VSC operations.
    2. If the skid control ECU detects that a system related to the hybrid control system is malfunctioning, it will prohibit operation of the TRAC and VSC system in order to prevent further malfunctions and to protect the system.
      Item Operation
      Malfunction in the ABS system ABS, BA, TRAC and VSC control prohibited
      Malfunction in the BA system ABS, BA, TRAC and VSC control prohibited
      Malfunction in the EBD system ABS, EBD, BA, TRAC and VSC control prohibited
      Malfunction in the TRAC system ABS, BA, TRAC and VSC control prohibited
      Malfunction in the VSC system ABS, BA, TRAC and VSC control prohibited
  2. FAIL-SAFE FUNCTION OF HYDRAULIC SYSTEM 
    1. If a malfunction is detected in the brake booster with master cylinder (skid control ECU or brake actuator) or an individual sensor, control will be stopped and brake effort will be generated by the brake booster with master cylinder (hydraulic brake booster).
    2. If brake control is stopped due to a malfunction in the hydraulic pressure source, the pressure generated in the master cylinder by the driver is applied to the wheel cylinders to ensure braking force.
      Item Operation
      Skid control ECU malfunction Brake booster with master cylinder (hydraulic brake booster) generated braking force
      Hydraulic pressure controlling components malfunction Brake booster with master cylinder (hydraulic brake booster) generated braking force
      Power supply components (Hydraulic pressure source) malfunction Braking force solely generated by the driver
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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