System Description [10/2014 - 09/2017]

1. The pre-collision system detects vehicles and obstacles in front of the vehicle and performs the following: 1) optimally uses system controls to avoid collisions; and 2) uses system controls to reduce impact during a collision.

1. Collision detection
   1. The driving support ECU assembly receives information on vehicles and obstacles in front of the vehicle from the millimeter wave radar sensor assembly. It determines in advance the possibility of collision and whether the collision can be avoided, based on the obstacle position, vehicle speed and road surface conditions.

      HINT: 

      For details about the system, see "OUTLINE OF PRE-COLLISION SYSTEM" and the outline of each control.

2. Component

   Component	Detection Content
   Millimeter wave radar sensor assembly	Obstacles in front

1. When operating according to millimeter wave radar sensor assembly detection:

   The millimeter wave radar sensor assembly detects vehicles and other objects on the road in front of the user's vehicle. The driving support ECU assembly determines if the possibility of a collision is high or if a collision is unavoidable based on obstacle position, vehicle speed and road surface conditions. If the driving support ECU assembly determines that the possibility of collision is high or that a collision is unavoidable, it transmits this information to the following areas via CAN communication:

   • Combination meter assembly (warning message) (activates pre-collision alarm)
   • Millimeter wave radar sensor assembly (warning buzzer) (activates pre-collision alarm)
   • Brake booster with master cylinder assembly (skid control ECU) (activates pre-collision brake assist)
   • Brake booster with master cylinder assembly (skid control ECU) (activates pre-collision brake)

1. When the system determines that there is a high possibility of colliding with an obstacle in front of the vehicle, the multi-information display and warning buzzer are used to warn the driver and help with collision avoidance.

1. The pre-collision brake assist operates depending on what the millimeter wave radar sensor assembly detects. The system then enters standby mode before a collision. When the driver depresses the brake pedal, brake fluid pressure is increased to improve fluid pressure response and improve the rate of deceleration.
2. Operating conditions
   1. Refer to the millimeter wave radar sensor assembly description under "Outline of Pre-collision System" (see above).
   2. When the driver depresses the brake pedal after the driving support ECU assembly determines that the possibility of a collision is high:

      Brake fluid pressure is increased at the same time the driver depresses the brake pedal.

1. The pre-collision brake operation is performed depending on what the millimeter wave radar sensor assembly detects.
2. Operating conditions
   1. Refer to the millimeter wave radar sensor assembly description under "Outline of Pre-collision System" (see above).
   2. When the driving support ECU assembly determines that a collision is unavoidable, the system performs brake control (pre-collision brake operation) to reduce the vehicle speed.

      When a preceding vehicle is detected, the system advances brake control (pre-collision brake operation) activation timing in order to increase speed reduction performance.

1. Pre-collision system sensitivity switch function
   1. The No. 2 combination switch assembly includes a pre-collision system switch. Each time the switch is pressed, the multi-information display sensitivity switch display changes between "Far", "Medium" and "Near", in that order to switch the sensitivity of the pre-collision system between 3 levels.

      HINT: 

      • The sensitivity setting display is shown for 6 seconds.
      • "Medium" is the default setting.
      Fig 1: View Of Multi-Information Display Sensitivity Switch Display Changes Between "Far", "Medium" And "Near"

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      *1	Far	*2	Medium
      *3	Near	-	-

2. Pre-collision system cancel function
   1. The No. 2 combination switch assembly includes a pre-collision system switch. When the switch is pressed and held for 3 seconds, the pre-collision system stops operation.

      HINT: 

      While the system is canceled, the multi-information display and PCS warning indicator are illuminated.

1. The integration control and panel assembly includes a VSC OFF switch. Turning the switch on cancels pre-collision brake assist control and pre-collision brake control operation.

   HINT: 

   After the switch is pressed, a warning message displays on the multi-information display of the combination meter assembly for 6 seconds and the PCS warning indicator illuminates.

HINT: 

Each function will operate when all items marked (◦) are satisfied.

• ◦: Operation condition is included
• x: Operation condition is not included
• *: Inoperative parts are different depending on malfunction areas

1. When the millimeter wave radar sensor assembly detects an obstacle in front of the vehicle under the following conditions, the driving support ECU assembly may determine that the possibility of a collision is high or a collision is unavoidable, and activate the pre-collision system. This activation of the system is not abnormal.
   Fig 2: View Of Obstacle In Front Of The Vehicle Under The Following Conditions

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	There are objects on the side of the road at the beginning of a curve (a guardrail, street light, billboard, etc.).	*b	Passing an oncoming vehicle on a curve.
   *c	When passing an oncoming vehicle while making a left turn.	*d	Crossing a narrow metal bridge.
   *e	There are metal objects on the road.	*f	Approaching a leading vehicle suddenly.
   *g	Approaching an electrical toll collection gate (reacts to bar).	*h	Crossing an overpass, traffic sign, signboard.
   *i	The vehicle height drastically changes (nose-up, nose-down).	*j	Misalignment of millimeter wave radar sensor assembly (reinstallation, collision, etc).
   *k	There is a billboard or sign at the top of an incline.	*l	There are metal objects at the bottom of a decline (a metal plate covering road construction, a mesh drain cover, a manhole, etc.).
   *m	Roughness in road surface.	*n	When passing through a tunnel.
   *o	When vehicle is tilted upwards (caused by towing a trailer or during emergency towing, a heavy load in the luggage compartment etc.).	-	-

   HINT: 

   • The pre-collision system will not activate when approaching safety cones or other plastic objects as they cannot be detected by the millimeter wave radar sensor assembly.
   • The pre-collision system may or may not activate when the millimeter wave radar sensor assembly detects the following objects: people, bicycles, motorcycles, trees, animals, snow fences, etc.
   • Detection performance may deteriorate under the following conditions.
     • On a tight curve or bumpy road
     • Something or someone suddenly emerges in the direction of travel of the driver's vehicle at a place such as an intersection
     • Another vehicle suddenly cuts in the traveling direction of the driver's own vehicle
     • In severe weather such as heavy rain, fog, snow or a sand storm
     • Vehicle is skidding sideways while the electronically controlled brake system is not operating
     • Vehicle height changes significantly (front of vehicle inclined either upward or downward)
     • An obstacle suddenly appears in front of the vehicle when the steering wheel is turned a large amount
     • Millimeter wave radar sensor assembly is misaligned (due to reinstallation or collision)

       Object Type	Example
       Objects that cannot be detected	Plastic items (safety cones)
       Objects that cannot be detected in a stable manner	People, bicycles, motorcycles, trees, animals, snow fences, etc.