DPB_a224 — Brake Boost Lost
Full alert identifier: DPB_a224_brakeBoostLost
Alert description
Brake boosting capability is lost in DPB system.
Potential impact
System will request Hydraulic Boost Compensation when driver pressed the brake pedal.
Set condition
Plunger Separation Valve or Plunger Overshoot Valve inoperable (aka huge leakage rate present in plunger circuit) OR no brake fluid OR wrong plunger configuration (as held in EEPROM), Fault is raised if Active System Tests (component STS) detect a latent fault that might jeopardize the hydraulic backup functionality. The first occurence of the fault may only be detected right after the start of a new OtherCycle, when in full hydraulic system and at earliest if any brake event has been absent since the start of a new OtherCycle. The system reaction to the presence of the fault is DPB Hydraulic Backup (without brake boost).
Clear condition
First ensure that DPB ECU has fallen asleep. Execute the start of a new OtherCycle. Wait for at least 30 s without exerting any brake intervention (i.e. no apply of the brake pedal, hand brake, APB, value added function or similar).
Check other alerts
With Service Mode Plus enabled, open Service Alerts → All. Review the other alerts for clues to the cause of DPB_a224.