Lexus NX: System Description

Lexus NX Service Manual / Brake / Parking Brake / Electric Parking Brake System / System Description

SYSTEM DESCRIPTION

SYSTEM DESCRIPTION

(a) The electric parking brake system electronically controls the parking brake lock and release operations using actuators.

The main functions are as follows:

Functions when vehicle stopped

When the electric parking brake switch (integration control and panel assembly) is pulled, the parking brake locks. When the electric parking brake switch (integration control and panel assembly) is pushed with the brake pedal or accelerator pedal depressed, the lock releases.
When the AUTO function (shift-linked function) is on, parking brake operation is linked with the shift lever, and when the shift lever is moved to P, the parking brake locks. When the shift lever is moved from P to a different position with the brake pedal depressed, the lock releases.
When the electric parking brake switch (integration control and panel assembly) is pulled for 3 seconds or more with the vehicle stopped, the AUTO function (shift-linked function) turns on (AUTO indicator light illuminates). When the switch is pressed and held for 3 seconds or more, the AUTO function turns off (AUTO indicator light turns off).
If a malfunction occurs in the electric parking brake switch (integration control and panel assembly) when the AUTO function (shift-linked function) is off, the AUTO function (shift-linked function) automatically operates to ensure operability.
HINT:

Only the release operation functions.

Other supplementary functions

When the driver side door is opened, the driver seat belt is unfastened, the engine hood is opened, or the back door is opened while the brake hold is operating (vehicle is stopped), or 3 minutes elapse after brake hold operates, the parking brake automatically locks.
When the brake pedal is depressed during the above conditions, the parking brake does not automatically lock.

When starting off, it is necessary to depress the accelerator pedal to release the parking brake.

HINT:

When the brake system malfunctions while brake hold is operating, the parking brake automatically locks.

When starting off, it is necessary to perform a release operation with the electric parking brake switch (integration control and panel assembly) to release the parking brake.

Emergency response function

When the vehicle is being driven, braking force is only generated according to the fluid pressure of the brake actuator while the electric parking brake switch (integration control and panel assembly) is being pulled up.
When the electric parking brake switch (integration control and panel assembly) is released, the brake fluid pressure of the brake actuator is released and the braking force decreases.

COMPONENTS OPERATION

(a) Parking brake ECU assembly:

(1) Operates the parking brake actuator assembly to lock or release the parking brake according to driver switch operation, the shift lever position and signals via CAN communication.

(b) Parking brake actuator assembly:

(1) Operates the motor according to commands from the parking brake ECU assembly, generates the necessary torque with the gears and transmits rotary torque to the rear brake calipers.

(1) Converts the parking brake actuator assembly rotary torque into driving force to bring the rear brake pads together to generate braking force. When the parking brake motor (parking brake actuator assembly) is stopped, the parked position is maintained with screw friction.

(d) Electric parking brake switch (Integration control and panel assembly):

(1) Detects driver switch operations and outputs signals to the parking brake ECU assembly.

(e) Brake warning light / yellow (minor malfunction):

(1) If the electric parking brake system is malfunctioning or a problem in another system causes the parking brake function to be limited, this light informs the driver.

(f) Parking brake indicator light (red):

(1) The parking brake indicator light (red) in the combination meter assembly illuminates when the parking brake is locked and turns off when the parking brake is released. Also, if the driver attempts to operate the electric parking brake when operation is not possible or parking force is insufficient, the light blinks.

(g) Electric parking brake switch indicator light:

(1) The electric parking brake switch indicator light in the electric parking brake switch (integration control and panel assembly) illuminates when the parking brake is locked and turns off when the parking brake is released.

(h) AUTO indicator light:

(1) The AUTO indicator light in the electric parking brake switch (integration control and panel assembly) informs the driver of whether AUTO function (shift-linked function) control is possible.

AUTO function (shift-linked function) on: Illuminates, AUTO function (shift-linked function) off: Turns off

(i) Multi-information display:

(1) If a malfunction occurs in the electric parking brake system and system control is not possible, the brake warning light / yellow (minor malfunction) and multi-information display are used to inform the driver. Also, an error displays for the driver.

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