PRE-COLLISION: PRE-COLLISION SYSTEM: SYSTEM DESCRIPTION; 2018 - 2020 MY Sienna [11/2017

Last Modified: 04-05-2023	6.11:8.1.0	Doc ID: RM1000000018YAW
Model Year Start: 2018	Model: Sienna	Prod Date Range: [11/2017 - ]
Title: PRE-COLLISION: PRE-COLLISION SYSTEM: SYSTEM DESCRIPTION; 2018 - 2020 MY Sienna [11/2017 - ]

SYSTEM DESCRIPTION

PRE-COLLISION SYSTEM DESCRIPTION

(a) The pre-collision system uses the pre-collision warning control, pre-collision brake assist control and pre-collision braking control to help avoid a collision or reduce the impact if it determines that the possibility of a collision is high or a collision is unavoidable based on the position and relative speed of an obstacle.

(b) The operation of this system can be turned off and on using the setting screen of the multi-information display.

HINT:

When the pre-collision system is turned off, the PCS warning light in the combination meter assembly will illuminate.

PRE-COLLISION SYSTEM SENSOR DESCRIPTION

(a) The millimeter wave radar sensor assembly and forward recognition camera detect the position and relative speed of preceding vehicles and pedestrians*. This information is sent to the driving support ECU to determine if the possibility of a collision is high or a collision is unavoidable.

HINT:

*: Depending on the vehicle destination and specifications, the pedestrian detection function may not be available.

FUNCTION OF MAIN COMPONENTS

COMPONENTS	FUNCTION
Millimeter Wave Radar Sensor Assembly	Radiates millimeter waves forward and uses reflected waves to detect the distance to, direction of, and relative speed of objects in front of the vehicle. Sends information (the distance to, direction of, and relative speed of detected objects) to the driving support ECU assembly.
Driving Support ECU Assembly	Determines if the possibility of a collision is high or a collision is unavoidable based on the signals from each sensor and sends brake request signals to the skid control ECU. Sends request signals to illuminate the PCS warning lights, display related information on the multi-information display in the combination meter assembly and sound a buzzer.
Forward Recognition Camera	Captures images of the area in front of the vehicle and processes them to detect preceding vehicles or pedestrians and sends information to the driving support ECU assembly.
Airbag Sensor Assembly (Yaw Rate and Acceleration Sensor)	Detects the yaw rate and acceleration of the vehicle and sends signals to the driving support ECU assembly.
Spiral Cable with Sensor Sub-assembly (Steering Angle Sensor)	Detects the steering angle and direction and sends signals to the driving support ECU assembly.
Vehicle Speed Sensor	Detects the wheel speed and sends signals to the skid control ECU.
Stop Light Switch Assembly	Detects the depression of the brake pedal and sends signals to the skid control ECU. Illuminates the stop lights based on the pre-collision braking control operation signal from the skid control ECU.
Steering Pad Switch Assembly	Used to turn the pre-collision system on and off. Can be used to change the pre-collision system sensitivity setting between "Far", "Mid", "Near".
VSC OFF Switch	Disables the pre-collision brake assist control and pre-collision braking control if pressed and held.
Brake Actuator Assembly (Skid Control ECU)	Performs pre-collision braking control based on brake request signals from the driving support ECU assembly. Sends wheel speed signals to the driving support ECU assembly. Detects the brake request signal and sends a signal to the stop light relay (stop light switch assembly).
Combination Meter Assembly	Displays "BRAKE!" on the multi-information display when the pre-collision warning control is being performed. Illuminates the PCS warning light when the pre-collision system is turned off. Illuminates the master warning light, blinks or illuminates the PCS warning light and displays an appropriate warning message on the multi-information display to inform the driver if a malfunction is detected in the pre-collision system.
Skid Control Buzzer Assembly	Sounds to warn the driver when the pre-collision warning control is operated.
Main Body ECU (Multiplex Network Body ECU)	Sends vehicle destination country information to the driving support ECU assembly.

OUTLINE OF PRE-COLLISION SYSTEM

(a) PRE-COLLISION WARNING:

(1) When the system determines that the possibility of a frontal collision is high, a buzzer will sound and a warning message will be displayed on the multi-information display to urge the driver to take evasive action.

(b) PRE-COLLISION BRAKE ASSIST:

(1) When the system determines that the possibility of a frontal collision is high, the system applies greater braking force in relation to how strongly the brake pedal is depressed.

(1) When the system determines that the possibility of a frontal collision is high, the system warns the driver. If the system determines that the possibility of a frontal collision is extremely high, the brakes are automatically applied to help avoid the collision or reduce the collision speed.

CAUTION:

If the vehicle is stopped by the operation of the pre-collision braking function, the pre-collision braking function operation will be canceled after approximately 2 seconds. Depress the brake pedal as necessary.
The pre-collision braking function may not operate if certain operations are performed by the driver. If the accelerator pedal is being depressed strongly or the steering wheel is being turned, the system may determine that the driver is taking evasive action and possibly prevent the pre-collision braking function from operating.

PRE-COLLISION SYSTEM CONTROL OPERATION

Control Operation

Control	Operating Condition	Transmitting ECU	Receiving ECU	Part Operated
Pre-collision warning	Possibility of a collision is high	Driving Support ECU Assembly	Combination Meter Assembly	Combination Meter Assembly (warning message) Skid Control Buzzer Assembly (warning buzzer)
Pre-collision brake assist	Possibility of a collision is high The brake pedal is depressed	Driving Support ECU Assembly	Combination Meter Assembly Skid Control ECU (Brake Actuator Assembly)	Combination Meter Assembly (warning message) Skid Control Buzzer Assembly (warning buzzer) Brake Actuator Assembly
Pre-collision braking	Possibility of a collision is extremely high	Driving Support ECU Assembly	Combination Meter Assembly Skid Control ECU (Brake Actuator Assembly)	Combination Meter Assembly (warning message) Skid Control Buzzer Assembly (warning buzzer) Brake Actuator Assembly

PRE-COLLISION SYSTEM OPERATION CONDITIONS

CAUTION:

Always observe the legal speed limit when driving on public roads.

CONTROL OPERATION CONDITIONS FOR EACH SPECIFICATION

Specification	Pre-collision Warning	Pre-collision Brake Assist (PBA)	Pre-collision Braking (PB)
1	The pre-collision system is ON. Vehicle speed is between approximately 7 and 110 mph (10 and 180 km/h). The relative speed between your vehicle and the vehicle or pedestrian ahead is approximately 7 mph (10 km/h) or more. For detecting a pedestrian, vehicle speed is between approximately 7 and 50 mph [10 and 80 km/h]	The pre-collision system is ON. The VSC is enabled. Vehicle speed is between approximately 20 and 110 mph (30 and 180 km/h). The relative speed between your vehicle and the vehicle or pedestrian ahead is approximately 20 mph (30 km/h) or more. For detecting a pedestrian, vehicle speed is between approximately 20 and 50 mph [30 and 80 km/h].	The pre-collision system is ON. The VSC is enabled. Vehicle speed is between approximately 7 and 110 mph (10 and 180 km/h). The relative speed between your vehicle and the vehicle or pedestrian ahead is approximately 7 mph (10 km/h) or more. For detecting a pedestrian, vehicle speed is between approximately 7 and 50 mph [10 and 80 km/h].
2	The pre-collision system is ON. Vehicle speed is between approximately 15 and 180 km/h (10 and 110 mph). The relative speed between your vehicle and the vehicle ahead is approximately 10 km/h (7 mph) or more.	The pre-collision system is ON. The VSC is enabled. Vehicle speed is between approximately 30 and 180 km/h (20 and 110 mph). The relative speed between your vehicle and the vehicle ahead is approximately 30 km/h (20 mph) or more.	The pre-collision system is ON. The VSC is enabled. Vehicle speed is between approximately 15 and 180 km/h (10 and 110 mph). The relative speed between your vehicle and the vehicle ahead is approximately 10 km/h (7 mph) or more.

CONTROLS AVAILABLE FOR EACH SPECIFICATION (REFERENCE)

Specification	Pre-collision Warning	Pre-collision Brake Assist (PBA)	Pre-collision Braking (PB)	Pedestrian Detection Function
1	Available	Available	Available	Available
2	Available	Available	Available	Not Available

Conditions under which the system may operate even if there is no possibility of a collision

(a) In some situations such as the following, the system may determine that there is a possibility of a frontal collision and operate.

When passing a vehicle or pedestrian*
When changing lanes while overtaking a preceding vehicle
When overtaking a preceding vehicle that is changing lanes
When overtaking a preceding vehicle that is making a left/right turn
When passing a vehicle in an oncoming lane that is stopped to make a right/left turn
When driving on a road where relative location to vehicle ahead in an adjacent lane may change, such as on a winding road
When rapidly closing on a vehicle ahead
If the front of the vehicle is raised or lowered, such as when the road surface is uneven or undulating
When approaching objects on the roadside, such as guardrails, utility poles, trees, or walls
When there is a vehicle, pedestrian*, or object by the roadside at the entrance of a curve
When driving on a narrow path surrounded by a structure, such as in a tunnel or on an iron bridge
When there is a metal object (manhole cover, steel plate, etc.), steps, or a protrusion on the road surface or roadside
When a crossing pedestrian approaches very close to the vehicle*
When passing through a place with a low structure above the road (low ceiling, traffic sign, etc.)
When passing under an object (billboard, etc.) at the top of an uphill road
When rapidly closing on an electric toll gate barrier, parking area barrier, or other barrier that opens and closes
When using an automatic car wash
When driving through or under objects that may contact the vehicle, such as thick grass, tree branches, or a banner
When the vehicle is hit by water, snow, dust, etc. from a vehicle ahead
When driving through steam or smoke
When there are patterns or paint on the road or a wall that may be mistaken for a vehicle or pedestrian*
When driving near an object that reflects radio waves, such as a large truck or guardrail
When driving near a TV tower, broadcasting station, electric power plant, or other location where strong radio waves or electrical noise may be present

*: Depending on the region in which the vehicle was sold, the pedestrian detection function may not be available.

Situations in which the system may not operate properly

(a) In some situations such as the following, a vehicle may not be detected by the millimeter wave radar sensor assembly and forward recognition camera, preventing the system from operating properly:

If an oncoming vehicle is approaching the vehicle
If a vehicle ahead is a motorcycle or bicycle
When approaching the side or front of a vehicle
If a preceding vehicle has a small rear end, such as an unloaded truck
If a preceding vehicle has a low rear end, such as a low bed trailer
If a vehicle ahead is carrying a load which protrudes past its rear bumper
If a vehicle ahead has extremely high ground clearance
If a vehicle ahead is irregularly shaped, such as a tractor or side car
If the sun or other light is shining directly on a vehicle ahead
If a vehicle cuts in front of the vehicle or emerges from beside a vehicle
If a vehicle ahead makes an abrupt maneuver (such as sudden swerving, acceleration or deceleration)
When suddenly cutting behind a preceding vehicle
When a vehicle ahead is not directly in front of the vehicle
When driving in inclement weather such as heavy rain, fog, snow or a sandstorm
When the vehicle is hit by water, snow, dust, etc. from a vehicle ahead
When driving through steam or smoke
When driving in a place where the surrounding brightness changes suddenly, such as at the entrance or exit of a tunnel
When a very bright light, such as the sun or the headlights of oncoming traffic, shines directly into the forward recognition camera
When the surrounding area is dim, such as at dawn or dusk, or while at night or in a tunnel
After the engine has started the vehicle has not been driven for a certain amount of time
While making a left/right turn and for a few seconds after making a left/right turn
While driving on a curve and for a few seconds after driving on a curve
If the vehicle is skidding
If the front of the vehicle is raised or lowered
If the wheels are misaligned
If a wiper blade is blocking the forward recognition camera
The vehicle is wobbling
The vehicle is being driven at extremely high speeds
When driving on a hill
If the millimeter wave radar sensor assembly or forward recognition camera is misaligned

(b) In some situations such as the following, sufficient braking force may not be obtained, preventing the system from performing properly:

If the braking functions cannot operate to their full extent, such as when the brake parts are extremely cold, extremely hot, or wet
If the vehicle is not properly maintained (brakes or tires are excessively worn, improper tire inflation pressure, etc.)
When the vehicle is being driven on a gravel road or other slippery surface

(c) Some pedestrians such as the following may not be detected by the millimeter wave radar sensor assembly and forward recognition camera, preventing the system from operating properly*:

Pedestrians shorter than approximately 3.2 ft. (1 m) or taller than approximately 6.5 ft. (2 m)
Pedestrians wearing oversized clothing (a rain coat, long skirt, etc.), making their silhouette obscure
Pedestrians who are carrying large baggage, holding an umbrella, etc., hiding part of their body
Pedestrians who are bending forward or squatting
Pedestrians who are pushing a stroller, wheelchair, bicycle or other vehicle
Groups of pedestrians which are close together
Pedestrians who are wearing white and look extremely bright
Pedestrians in the dark, such as at night or while in a tunnel
Pedestrians whose clothing appears to be nearly the same color or brightness as their surroundings
Pedestrians near walls, fences, guardrails, or large objects
Pedestrians who are on a metal object (manhole cover, steel plate, etc.) on the road
Pedestrians who are walking fast
Pedestrians who are changing speed abruptly
Pedestrians running out from behind a vehicle or a large object
Pedestrians who are extremely close to the side of the vehicle (outside rear view mirror, etc.)

*: Depending on the region in which the vehicle was sold, the pedestrian detection function may not be available.

If the PCS warning light flashes or illuminates and a warning message is displayed on the multi-information display

HINT:

For details on the operation of the PCS warning light and displayed warning messages, refer to Diagnosis System.

Click here

(a) The pre-collision system may be temporarily unavailable or there may be a malfunction in the system.

(b) In the following situations, the warning light will turn off, the message will disappear and the system will become operational when normal operating conditions return:

When the millimeter wave radar sensor assembly or forward recognition camera or the area around either sensor is hot, such as in the sun
When the millimeter wave radar sensor assembly or forward recognition camera or the area around either sensor is cold, such as in an extremely cold environment
When the millimeter wave radar sensor assembly or front grille emblem is dirty or covered with snow, etc.
When the part of the windshield glass in front of the forward recognition camera is fogged up or covered with condensation or ice
If the forward recognition camera is obstructed, such as when the hood is open or a sticker is attached to the windshield near the forward recognition camera

If VSC is disabled

(a) If VSC is disabled, the pre-collision brake assist and pre-collision braking functions are also disabled.

(b) The PCS warning light will turn on and "VSC Turned Off Pre-collision Brake System Unavailable" will be displayed on the multi-information display.