ABS FUNCTION : System Description

• By preventing wheel lock through brake force (brake fluid pressure) control that is electronically controlled by detecting wheel speed during braking, stability during emergency braking is improved so that obstacles can be easily bypassed by steering operation.
• During braking, control units calculates wheel speed and pseudo-vehicle speed, and transmits pressure increase, hold or decrease signals to actuator portion according to wheel slip status.
• The following effects are obtained by preventing wheel lock during braking.
  • Vehicle tail slip is prevented during braking when driving straight.
  • Understeer and oversteer tendencies are moderated during braking driving on a corner.
  • Obstacles may be easily bypassed by steering operation during braking.
• CONSULT-III can be used to diagnose the system diagnosis.
• Fail-safe function is adopted. When a malfunction occurs in ABS function, the control is suspended for VDC function, TCS function, ABS function, hill start assist function, Rise-up & Build-up function, Brake force distribution function and Active trace control function. The vehicle status becomes the same as models without VDC function, TCS function, ABS function, hill start assist function, Rise-up & Build-up function, Brake force distribution function and Active trace control function. However, EBD function is operated normally. Refer to "FAIL-SAFE ".
  NOTE:

  • ABS has the characteristic as described here, This is not the device that helps reckless driving.
  • To stop vehicle efficiently, ABS does not operate and ordinary brake operates at low speed [approx. 5 to 10 km/h (3 to 6 MPH) or less, but differs subject to road conditions).
    Fig 1: ABS Function Diagram

    Courtesy of NISSAN MOTOR CO., U.S.A.
  • Self-diagnosis is performed immediately after when engine starts and when vehicle initially is driven [by vehicle speed approx. 15 km/h (9 MPH)]. Motor sounds are generated during self-diagnosis. In addition, brake pedal may be felt heavy when depressing brake pedal lightly. These symptoms are not malfunctions.

SYSTEM DIAGRAM

Fig 2: ABS Operation Diagram

Courtesy of NISSAN MOTOR CO., U.S.A.

INPUT SIGNAL AND OUTPUT SIGNAL

Major signal transmission between each unit via communication lines is shown in the following table.