Hydraulic Control Assembly - Antilock Brakes: Description and Operation

HYDRAULIC CONTROL UNIT (HCU)
ABS control steps
PHASE 0: Outside of ABS
PHASE 1: Pressure decreasing condition
PHASE 2: Pressure holding condition
PHASE 3: Pressure increasing condition
PHASE 4: Pressure decreasing condition
PHASE 5: Pressure decreasing condition

Basic control
PHASE 0-PHASE 1:
When ABS ECU detects the wheel locking, ABS ECU changes PHASE 0 to PHASE 1.
PHASE 1-PHASE 2:
If wheel cylinder liquid pressure is decreased, ABS ECU changes PHASE 1 to PHASE 2.
PHASE 2-PHASE 3:
If it is judged the there is no lock phenomenon in wheel, ABS ECU changes PHASE 2 to PHASE 3.
PHASE 2-PHASE 4:
If wheel cylinder liquid pressure is cascading on the deceleration section, ABS ECU changes PHASE 2 to PHASE 4.
PHASE 2-PHASE 5:
If wheel cylinder liquid pressure is cascading on the acceleration section, ABS ECU changes PHASE 2 to PHASE 5.