Toyota Tacoma manuals

Toyota Tacoma 2015-2018 Service Manual: System Description

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 a preceding vehicle.

(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 millimeter wave radar sensor assembly to determine if the possibility of a collision is high or a collision is unavoidable.

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.
  • 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 (master cylinder solenoid)*1 or skid control ECU (brake actuator assembly)*2.
  • Sends request signals to illuminate the PCS warning light, 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 millimeter wave radar sensor assembly.

Yaw Rate Sensor (Airbag Sensor Assembly)

Detects the yaw rate and acceleration of the vehicle and sends signals to the millimeter wave radar sensor assembly.

Steering Angle Sensor (Spiral Cable with Sensor Sub-assembly)

Detects the steering angle and direction, and sends signals to the millimeter wave radar sensor assembly.

Vehicle Speed Sensor

Detects the wheel speed and sends signals to the skid control ECU (master cylinder solenoid)*1 or skid control ECU (brake actuator assembly)*2.

Stop Light Switch Assembly

  • Detects the depression of the brake pedal and sends signals to the skid control ECU (master cylinder solenoid)*1 or skid control ECU (brake actuator assembly)*2.
  • Illuminates the stop lights based on the pre-collision braking control operation signal from the skid control ECU (master cylinder solenoid)*1 or skid control ECU (brake actuator assembly)*2.

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" and "Near".

VSC OFF Switch

Disables the pre-collision brake assist control and pre-collision braking control if pressed and held.

Skid Control ECU (Master Cylinder Solenoid)*1 or Skid Control ECU (Brake Actuator Assembly)*2

  • Performs pre-collision braking control based on brake request signals from the millimeter wave radar sensor assembly.
  • Sends wheel speed signals to the millimeter wave radar sensor 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, flashes 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.

Main Body ECU (Multiplex Network Body ECU)

Sends vehicle destination country information to the millimeter wave radar sensor assembly.

  • *1: for Hydraulic Brake Booster
  • *2: for Vacuum Brake Booster

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.

(c) Pre-collision Braking:

(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 collision is extremely high, the brakes are automatically applied to help avoid the frontal collision or reduce the collision speed.

HINT:

  • 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

Millimeter Wave Radar Sensor Assembly

Combination Meter Assembly

  • Combination Meter Assembly (warning message)
  • Skid Control Buzzer (warning buzzer)

Pre-collision brake assist

  • Possibility of a collision is high
  • The brake pedal is depressed

Millimeter Wave Radar Sensor Assembly

  • Combination Meter Assembly
  • Skid control ECU (Master Cylinder Solenoid)*1 or Skid Control ECU (Brake Actuator Assembly)*2
  • Combination Meter Assembly (warning message)
  • Skid Control Buzzer (warning buzzer)
  • Brake Actuator Assembly

Pre-collision braking

Further strong possibility of collision

Millimeter Wave Radar Sensor Assembly

  • Combination Meter Assembly
  • Skid control ECU (Master Cylinder Solenoid)*1 or Skid Control ECU (Brake Actuator Assembly)*2
  • Combination Meter Assembly (warning message)
  • Skid Control Buzzer (warning buzzer)
  • Brake Actuator Assembly
  • *1: for Hydraulic Brake Booster
  • *2: for Vacuum Brake Booster

PRE-COLLISION SYSTEM OPERATION CONDITIONS

CAUTION:

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

Control Operation Conditions for Each Specification

Pre-collision Warning

Pre-collision Brake Assist (PBA)

Pre-collision Braking (PB)

  • The pre-collision system is ON.
  • Vehicle speed is between approximately 7 and 110 mph (10 and 180 km/h).
  • The relative speed to a preceding vehicle 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 to a preceding vehicle 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 to a preceding vehicle 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).

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.

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 your 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 your 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 your 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 your 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 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.).

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

(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 a millimeter wave radar sensor assembly 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.
  • When the millimeter wave radar sensor assembly is performing beam axis alignment correction after detecting a misaligned beam axis.

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.

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