Toyota Tundra Service Manual: System Description

SYSTEM DESCRIPTION

AUTOMATIC LIGHT CONTROL SYSTEM

(a) When the light control switch is in the Auto position, the automatic light control system detects ambient light levels and controls the headlights, taillights, front fog lights (w/ Front Fog Light) parking lights, front side marker lights and license plate lights.

LIGHT AUTO TURN-OFF SYSTEM

(a) The light auto turn-off system is used to prevent the exterior lights from being accidentally left on (headlights, taillights, front fog lights (w/ Front Fog Light), parking lights, license plate lights and front side marker lights).

(1) This system has the following function.

Function

Outline

Delay function

The exterior lights automatically turn off after 30 seconds when all of the following conditions are met:

  • The low beam headlights are on (light control switch is in Auto position).
  • The ignition switch is turned from ON to off.
  • All doors are closed after any of the doors being open.

DAYTIME RUNNING LIGHT SYSTEM

(a) The daytime running light system is designed to automatically illuminate the headlights (high intensity parking lights), during the daytime to make the car more visible to other vehicles.

  • The main body ECU (multiplex network body ECU) controls this system.
  • This system is enabled when the conditions below are met:
    • The ignition switch is ON.
    • An engine speed signal is input (the engine is running).
    • Parking brake is released.
    • Headlight dimmer switch not in the DRL off position. (w/ DRL Off Switch)
    • Light control switch is in the off (w/o DRL Off Switch), Tail or Auto position (and the low beam headlights are not turned on via the automatic light control system).

AUTOMATIC HIGH BEAM SYSTEM (w/ Automatic High Beam System)

(a) General

The automatic high beam system enhances the illumination of the area in front of the vehicle to improve visibility for the driver. It works by detecting light from the front of the vehicle, using the forward recognition camera, and turns the high beams of the headlights on or off automatically.

(b) Function of Main Components

Component

Outline

Forward recognition camera

Determines when to turn the high beams on and off after identifying the lights of oncoming vehicles, preceding vehicles and other lights from the picture information of its camera sensor. Then, it sends high beam request signals to the main body ECU (multiplex network body ECU) via CAN communication.

Airbag sensor assembly

Outputs yaw rate information to the forward recognition camera.

Brake actuator assembly (skid control ECU)

Outputs the information about the speed of the wheels. This information is used by the forward recognition camera to turn the high beams on and off.

Combination meter assembly

Turns on the automatic high beam indicator light and displays a message on the multi-information display based on an indicator illumination request signal from the main body ECU (multiplex network body ECU).

HINT:

  • When an automatic high beam system malfunction is detected, the automatic high beam indicator light turns off and "Headlight System Malfunction Visit Your Dealer" is displayed on the multi-information display.
  • The automatic high beam indicator light illuminates to inform the driver when the automatic high beam system is active.

Main body ECU (multiplex network body ECU)

  • Determines whether the automatic high beam system is in standby mode based on the headlight dimmer switch high position signal, light control switch Auto or Head position signal and auto high beam switch signal, and sends an indicator illumination request signal and message display request signal to the combination meter assembly.
  • Receives the high beam illumination request signal from the forward recognition camera and changes between the high beams and low beams.
  • Performs illumination control for the automatic high beam system and stores Diagnostic Trouble Codes (DTCs) when the system malfunctions.

Auto high beam switch

Enables or disables the automatic high beam system.

Headlight dimmer switch assembly

Outputs light control switch information to the main body ECU (multiplex network body ECU).

(c) Basic Function

(1) When all of the following conditions are met, the automatic high beam system is activated and the automatic high beam indicator light turns on:

  • Turn the ignition switch to ON.
  • The light control switch is in the Auto or Head position and the low beam headlights are on.
  • The headlight dimmer switch is in the high position.
  • The auto high beam switch is on.

(2) When all of the following conditions are met, the high beams automatically turn on after a short delay:

  • Vehicle speed is more than approximately 34 km/h (21 mph).
  • The area in front of the vehicle is dark.
  • There are no oncoming vehicles with headlights on.
  • There are no preceding vehicles with taillights on.
  • There are few streetlights along the street ahead.

(3) When any of the following conditions are met, the high beams automatically turn off after a short delay:

  • Vehicle speed is less than approximately 27 km/h (17 mph).
  • There are oncoming vehicles with headlights on.
  • There are preceding vehicles with taillights on.
  • Light from streetlights ahead is higher than a specified threshold.

(4) When any of the following conditions are met, the automatic high beam system will be canceled and the indicator light will turn off:

  • Turn the ignition switch off.
  • The light control switch is turned to any position except the Auto or Head position.
  • The headlight dimmer switch is moved to the low position.
  • The auto high beam switch is off.

HINT:

It is possible to manually turn the high beams on and off by performing either of the following operations:

  • When changing the high beams controlled by the automatic high beam system to the low beams manually, move the headlight dimmer switch to the low position. The automatic high beam system will be canceled and the low beams will be turned on. To enable the automatic high beam system again, move the headlight dimmer switch to the high position.
  • When changing the low beams controlled by the automatic high beam system to the high beams manually, turn the auto high beam switch off. The automatic high beam system will be canceled and the high beams will be turned on. To enable the automatic high beam system again, turn the auto high beam switch on.

HINT:

The automatic high beam system monitors the area in front of the vehicle using the forward recognition camera and makes a judgment to turn on the high beams when the surrounding area is dark (there are no headlights from oncoming vehicles and no taillights from preceding vehicles). High beam control limitations:

  • When the surrounding area is not dark enough, the high beams will not turn on even if the low beam headlights are turned on by the automatic light control system and the automatic high beam indicator light on the combination meter assembly illuminates. (The light level sufficient to turn the auto low beams on is not the same as the light level required to automatically change the low beams to high beams.)
  • When an oncoming vehicle suddenly appears at a sharp curve or a vehicle crosses the path of the vehicle, the high beams may remain on.
  • When the fog lights of an oncoming vehicle are detected, the high beams may be turned off.
  • The timing of the high beams turning on and off may differ depending on the brightness of headlights or fog lights from oncoming vehicles or the taillights of preceding vehicles.
  • The timing of the high beams turning on and off may differ between normal conditions (good weather) and when driving on wet, frozen or snowy roads.
  • The timing of the high beams turning on and off may differ depending on the number of occupants and amount of cargo present.
  • Be aware that on some occasions, the high beams may switch on and off unexpectedly.

HINT:

Forward recognition camera continually monitors the light level in the area in front of the vehicle. There is a delay in turning on the high beams. Even when there is no ambient light, the high beams will not turn on immediately. The delay will vary depending on the situation.

MANUAL HEADLIGHT BEAM LEVEL CONTROL SYSTEM

(a) The manual headlight beam level control system controls each headlight leveling motor based on the headlight leveling switch operation in order to change the headlight reflector angle.

ILLUMINATION CONTROL SYSTEM (Illuminated Entry System)

HINT:

Perform this inspection with the interior dome light switch assembly, roof console box assembly (front interior light) and No. 1 room light assembly (rear interior light) are DOOR position.

(a) The illuminated entry system has the following control functions:

Control

Outline

Lighting

Door Lock/Unlock-linked

When any door is unlocked, the items listed to the right turn on.

  • Roof console box assembly (front interior light)
  • No. 1 room light assembly (rear interior light)
  • Foot light bulb (w/ Foot Light)
  • Transponder key coil (w/ Ignition Key Cylinder Light)

When all doors are locked, the items listed to the right turn off.

  • Roof console box assembly (front interior light)
  • No. 1 room light assembly (rear interior light)
  • Foot light bulb (w/ Foot Light)
  • Transponder key coil (w/ Ignition Key Cylinder Light)

Door Open/Close-linked

When any door is opened, the items listed to the right turn on.

  • Roof console box assembly (front interior light)
  • No. 1 room light assembly (rear interior light)
  • Foot light bulb (w/ Foot Light)
  • Transponder key coil (w/ Ignition Key Cylinder Light)

When all doors are closed, the items listed to the right turn off.

  • Roof console box assembly (front interior light)
  • No. 1 room light assembly (rear interior light)
  • Foot light bulb (w/ Foot Light)
  • Transponder key coil (w/ Ignition Key Cylinder Light)

Ignition Switch-linked

When the ignition switch is turned from ACC or ON to off, the items listed to the right turn on.

  • Roof console box assembly (front interior light)
  • No. 1 room light assembly (rear interior light)
  • Foot light bulb (w/ Foot Light)
  • Transponder key coil (w/ Ignition Key Cylinder Light)

BATTERY SAVING CONTROL SYSTEM

(a) The battery saving control system has the following control functions:

Control

Outline

Lighting

Basic function

When 20 minutes elapse after the ignition switch is turned from ACC or ON to off and the lights that operate remain on, the lights are turned off.

HINT:

Battery saving control is canceled when any of the following operations is performed before the lights are turned off by battery saving control. After the operation is performed, the lights remain on for another 20 minutes and then the lights are turned off.

  • The ignition switch is turned to ACC or ON.
  • Any door is opened and closed.
  • The luggage compartment door is opened and closed.
  • Any door is unlocked.
  • Roof console box assembly (front interior light)
  • No. 1 room light assembly (rear interior light)
  • Foot light bulb (w/ Foot Light)
  • Transponder key coil (w/ Ignition Key Cylinder Light)

Interior light auto cut function

When 20 minutes elapse after the ignition switch is turned from ACC or ON to off and the lights that operate remain on, the lights are turned off.

HINT:

Battery saving control is canceled when any of the following operations is performed before the lights are turned off by battery saving control. After the operation is performed, the lights remain on for another 20 minutes and then the lights are turned off.

  • The ignition switch is turned to ACC or ON.
  • Roof console box assembly (front interior light)
  • No. 1 room light assembly (rear interior light)
  • Visor assembly (w/ Vanity Light)
  • Foot light bulb (w/ Foot Light)
  • Transponder key coil (w/ Ignition Key Cylinder Light)
    Problem Symptoms Table

    System Diagram

    See More:

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