SECONDARY COLLISION REDUCTION

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Purpose

• The Secondary Collision Reduction is a part of the electronically controlled brake system functions which operates the automatic brakes and flashes the hazard warning lights when the vehicle is hit while it is stopped and moved by the impact to avoid the occurrence of a secondary collision.

Warning

• The secondary collision reduction performs the brake control, however, it is not a system which guarantees collision prevention under all conditions. Because deceleration by the brake control is limited.

Note

• The secondary collision reduction is a system for assisting driver operations. Accordingly, if the conditions for the secondary collision reduction are met, or even when the secondary collision reduction is operating, if the driver operates the steering wheel, accelerator pedal, and the brake pedal, the driver’s operations take precedence and the secondary collision reduction operation is canceled.

Function

• The secondary collision reduction functions are categorized as follows:

― When the SAS control module determines a collision while the vehicle is stopped, it flashes the hazard warning indicator lights automatically.

• Flashing of the hazard warning indicator lights is originally equipped on all models.

― Brake control which operates the automatic brakes when the vehicle is hit while it is stopped and moved by the impact.

• The brake control is equipped along with smart city brake support (SCBS).

Construction

Solenoid valve operation table

Pressure feed valve		TMC cut valve		Inlet solenoid valve				Outlet solenoid valve				Simulator valve	Linear actuator
LF—RR	RF—LR	LF—RR	RF—LR	LF	RF	LR	RR	LF	RF	LR	RR	Simulator valve	Linear actuator
ON (open)		ON (closed)		OFF (open)				OFF (closed)				OFF (open)	Operation

Hydraulic circuit diagram

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Block diagram

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Operation

Hazard warning operation

• When the detecting vehicle is hit by another vehicle and the SAS control module determines a collision, a hazard warning indicator light request signal (1) is output from the SAS control module to the BCM.

• When the BCM receives the hazard warning indicator light request signal, it flashes (2) the hazard warning indicator lights automatically to caution surrounding vehicles.

• All the hazard warning indicator lights flash automatically while the hazard warning indicator lights are flashing. When the hazard warning switch is pressed 2 times, this operation is canceled.

Brake control operation

• Operation conditions (any of the following conditions must be met):

― The selector lever is in the P position. (ATX)

― The parking brake is applied.

― The brake pedal is depressed. (the electronically controlled brake unit monitors the brake fluid pressure)

• When any of the operation conditions is met and the SAS control module detects a collision with another vehicle, it outputs a brake control request signal (3) to the electronically controlled brake unit. (At the same time, it also outputs a hazard warning request signal to the BCM).

• The electronically controlled brake unit energizes the traction control and the stability control solenoid valves to switch the hydraulic circuits, and at the same time, it operates the pump motor to activate the pump so that the brake fluid pressure is lead to the caliper piston and the automatic brakes are operated (4). At the same time, the electronically controlled brake unit outputs a brake light signal to the BCM (5).

• While the brake control is operating, turns on the brake lights automatically (6).

• Cancel condition (any of the following conditions must be met):

― The engine is stopped (the ignition is switched off).

― Approx. 1.5 s has elapsed since the vehicle was stopped by the brake control.

― The accelerator pedal opening angle exceeds approx. 70%.

― Brake force greater than that generated by the brake control is input via the brake pedal.

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Caution

• The secondary collision reduction does not operate if the electronically controlled brake system has a malfunction and the DSC control is inhibited.

• The secondary collision reduction may not operate in the case of a low-speed collision in which the air bags do not deploy.

• The secondary collision reduction may not operate if the vehicle speed exceeds approx. 50 km/h because of the first collision.

• The secondary collision reduction does not operate if the components of the SAS control module and the electronically controlled brake system are significantly damaged by the first collision.