ABS FUNCTION : System Description

WARNING: This page is about a different car, the 2011 Infiniti QX56. However, it is still accessible from the selected car via links, so may be relevant.

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.
Slight vibrations are felt on the brake pedal and the operation noises occur, when ABS function operates. This is not a malfunction because it is caused by ABS function that is normally operated.
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, hill start assist function and brake limited slip differential (BLSD) function. The vehicle status becomes the same as models without VDC function, TCS function, ABS function, hill start assist function and brake limited slip differential (BLSD) function. However, EBD function is operated normally. Refer to "FAIL-SAFE ".

Fig 1: Identifying ABS Function
Courtesy of NISSAN MOTOR CO., U.S.A.
NOTE:
- ABS has the characteristic as described here, but it 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 (3.1 to 6.2 MPH) or less, but differs subject to road conditions).
- Self-diagnosis is performed immediately after when engine starts and when vehicle initially is driven [by vehicle speed approx. 15 km/h (9.3 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

NOTE: Transfer control unit is applied to models with 4WD system.

Fig 2: ABS - System 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.

SIGNAL DESCRIPTION

Component

Signal description

Yaw rate/side/decel G sensor

Mainly transmits the following signals to ABS actuator and electric unit (control unit) via communication line⁽¹⁾.

Yaw rate signal
Side G sensor signal
Decel G sensor signal

Transfer control unit⁽²⁾

Mainly transmits the following signals to ABS actuator and electric unit (control unit) via CAN communication.

Current 4WD mode signal

Combination meter

Mainly receives the following signals from ABS actuator and electric unit (control unit) via CAN communication.

ABS warning lamp signal

⁽¹⁾	Communication line between yaw rate/side/decal G sensor and ABS actuator and electric unit (control unit)

⁽²⁾	Models with 4WD system