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Home >> Toyota >> 2021 >> Mirai Limited >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Electronically Controlled Brake System - Diagnostic Codes (3 Of 4) >> Electronically Controlled Brake System >> DTC C1391-00: Abnormal Leak in Accumulator [11/2020 - ] >> Description

DTC C1391-00: Abnormal Leak in Accumulator [11/2020 - ]: Description

This DTC is stored if internal or external brake fluid leaks are detected due to improper sealing in the brake booster with master cylinder assembly or brake booster pump assembly. Internal leaks are suspected if the pump motor operates frequently without braking.

DTC No. Detection Item DTC Detection Condition Trouble Area DTC Output from Priority Note
C1391-00 Abnormal Leak in Accumulator Either of the following is detected:
  • When the brake pedal is not depressed and the pump motor is operating, the accumulator pressure sensor value does not increase a certain number of times.
  • When the brake pedal is not depressed and the pump motor is not operating, the accumulator pressure sensor decrease rate exceeds a certain threshold a certain number of times.
  • Brake fluid leaks
  • Brake booster with master cylinder assembly

    (Malfunctioning internal seal etc.)

  • Brake booster pump assembly

    (Accumulator internal gas pressure decrease, etc.)

Brake Booster A Output ECU: No. 1 skid control ECU (brake booster with master cylinder assembly)
C1391-00 DTC DETECTION CONDITIONS

  Vehicle Condition
Pattern 1 Pattern 2
Diagnosis Condition When the brake pedal is not depressed and the pump motor is operating ◦ -
When the brake pedal is not depressed and the pump motor is not operating - ◦
Malfunction Status The accumulator pressure sensor value does not increase a certain number of times ◦ -
The accumulator pressure sensor decrease rate exceeds a certain threshold a certain number of times. - ◦
Detection Time - -
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.