ABS-ECU



  • By integrating ABS-ECU into the hydraulic unit, no wiring harness for sending drive signal of the solenoid valve and pump motor is required, assuring higher reliability.
  • By incorporating the G-sensor <4WD>, no sensor harness is required, enhancing the reliability.
  • Self-diagnostic and memory functions are integrated into ABS-ECU. If any malfunction is detected by the self-diagnostic function, ABS-ECU activates a fail-safe function and illuminates the ABS warning lamp and brake warning lamp*.
    note *: The brake warning lamp is used as the EBD control warning lamp.
  • ABS-ECU detects vehicle speed from the signals of the wheel speed sensor and its incorporated G sensor <4WD>, recognizes the wheel rotation status, estimates the wheel slip condition based on the preprogrammed algorithm, and then controls the solenoid valve in the hydraulic unit so that the wheels do not lock.

ABS fluid pressure control


ABS control cycle


  1. The ABS-ECU calculates the speed and deceleration of each wheel based on the signals from the four wheel speed sensors and the G sensor <4WD> incorporated in the ABS-ECU, and estimates the vehicle speed at that time.
  2. When the brake pedal is depressed, the brake fluid pressure applied to the wheel cylinder increases, and the wheel speed decreases. When the difference between the wheel speed and vehicle speed increases, and the vehicle deceleration goes below the specified value (Point A), ECU determines that the wheels are about to be locked. At this time, ECU reduces the brake fluid pressure by outputting the pressure decrease signal to the solenoid valves (IN, OUT). (between a and b)
  3. When the vehicle deceleration and wheel speed begin recovery, and the vehicle speed reaches the point B, ECU outputs the pressure hold signal to maintain the wheel cylinder fluid pressure. (between b and c)
  4. When the wheel speed deceleration is further recovered and overpasses the point C, ECU determines that the wheel lock possibility has been eliminated and increases the brake fluid pressure by outputting the pressure increase signal again. (between c and d)
  5. Brake fluid pressure is controlled by repeating the increase and hold of the pressure. (between d and e)
  6. When the wheel deceleration goes below the threshold again, ABS-ECU controls the brake fluid pressure by repeating the cycle (Step 2 to 5).

EBD fluid pressure control





INITIAL CHECK


*
note *: The ABS warning lamp may stay on after the ignition switch is turned ON until the startup vehicle speed reaches approximately 10 km/h. As far as ABS-ECU memorizes any diagnosis code related to the wheel speed sensor malfunction recorded during the previous ignition ON status, ABS-ECU continues illuminating the ABS warning lamp until it verifies that the malfunction for that code is resolved (startup check).

STARTUP CHECK



1.*

note *: Initial startup indicates a first startup after the system has started.
2.

CONSTANT CHECK



1.



2.

3.



4.

FAIL-SAFE FUNCTION


*
note *: The brake warning lamp is used as EBD control warning lamp.

DIAGNOSTIC FUNCTION




  • Diagnosis code set
  • Service data output
  • Actuator test
  • Freeze frame data output