- 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 combination switch assembly (automatic high beam main 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.
Lexus NX: System Description
Lexus NX Service Manual / Vehicle Exterior / Lighting (ext) / Automatic High Beam System / System Description
SYSTEM DESCRIPTION
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 ECU assembly | Outputs yaw rate information to the forward recognition camera. |
| Brake booster with master cylinder 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:
|
| Main body ECU (multiplex network body ECU) | |
| Combination switch assembly (automatic high beam main 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 power switch on (IG).
- 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 low position.
- The combination switch assembly (automatic high beam main 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 power 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 high position.
- The combination switch assembly (automatic high beam main 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 combination switch assembly (automatic high beam main 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 combination switch assembly (automatic high beam main 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.
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*: Use the Techstream.
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