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Home >> Toyota >> 2021 >> Mirai Limited >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Electronically Controlled Brake System - Diagnostic Codes (2 Of 4) >> Electronically Controlled Brake System >> DTC C12F8-12: ECB Solenoid Control "A" Circuit Short to Battery; DTC C12F8-14: ECB Solenoid Control "A" Circuit Short to Ground or Open [11/2020 - ] >> Description

DTC C12F8-12: ECB Solenoid Control "A" Circuit Short to Battery; DTC C12F8-14: ECB Solenoid Control "A" Circuit Short to Ground or Open [11/2020 - ]: Description

The main relay is built into the No. 1 skid control ECU (brake booster with master cylinder assembly).

The main relay supplies power to the switching solenoid and the linear solenoid.

The main relay remains on for approximately 3 minutes after the ignition switch is turned off and the input of brake pedal operation signals stops, and supplies power to the system to keep it ready to operate.

DTC No. Detection Item DTC Detection Condition Trouble Area DTC Output from Priority Note
C12F8-12 ECB Solenoid Control "A" Circuit Short to Battery When there is a main relay off command from the ECU, 3.5 V or more is detected at terminal BS for 4.5 seconds or more.
  • Short in main relay circuit
  • Main relay internal stuck
  • Wire harness and connector
  • No. 1 skid control ECU (brake booster with master cylinder assembly)
Brake Booster A
  • Output ECU: No. 1 skid control ECU (brake booster with master cylinder assembly)
  • ECB: Electronically Controlled Brake System
C12F8-14 ECB Solenoid Control "A" Circuit Short to Ground or Open Either of the following is detected:
  • When the ignition switch is turned to ON (READY):

    The BS terminal voltage is less than 3.3 V for 0.05 seconds or more, when the IG1 terminal voltage is 9.5 V or more and operation of the main relay is requested.

  • When the ignition switch is off:

    The BS terminal voltage is less than 3.3 V for 0.05 seconds or more, when operation of the main relay is requested.

  • Open or short in main relay circuit
  • Wire harness and connector
  • No. 1 skid control ECU (brake booster with master cylinder assembly)
Brake Booster A
  • Output ECU: No. 1 skid control ECU (brake booster with master cylinder assembly)
  • ECB: Electronically Controlled Brake System
C12F8-14 DTC DETECTION CONDITIONS

  Vehicle Condition
Pattern 1 Pattern 2
Diagnosis Condition When the ignition switch is turned to ON (READY) -
When the IG1 terminal voltage is 9.5 V or more -
When the ignition switch is off -
Malfunction Status The BS terminal voltage is less than 3.3 V and operation of the main relay is requested
Detection Time 0.05 seconds or more. 0.05 seconds or more.
Number of Trips 1 trip 1 trip

HINT: 

DTC will be output when conditions for either of the patterns in the table above are met.