DESCRIPTION & OPERATION
Note. Some models incorporate a multiplex control system. Before proceeding, ensure multiplex control system operation is okay, and no Diagnostic Trouble Codes (DTC) are set. See appropriate MULTIPLEX CONTROL SYSTEMS article.
When headlight switch is in AUTO position, system automatically illuminates low-beam headlights (and taillights) when needed. During daylight hours, the system automatically turns headlights off. If driver leaves headlight switch in AUTO position and turns ignition off, headlights will turn off when driver's door is opened. If headlights illuminate too early or too late, system sensitivity can be adjusted. See AUTOMATIC LIGHT CONTROL SENSOR under ADJUSTMENTS.
When intensity of light decreases sufficiently, light sensor internally grounds coil circuit of headlight relay (through headlight switch), causing headlight relay contacts to close and supply power to headlights. When intensity of light increases sufficiently, light sensor interrupts the internal connection.
When driver's door is open, light sensor detects closed contacts in door courtesy switch. Light sensor uses this signal to turn headlights off, if headlight switch is in AUTO position when ignition is turned off.
On GS300, GS400 and LS400 models, automatic headlight system is controlled by driver's door ECU and body control ECU.
SYSTEM OPERATION TEST
- Turn ignition on. Turn light control switch to AUTO position. Gradually cover automatic light control sensor. Headlights and instrument cluster lights should illuminate. Gradually uncover automatic light control sensor. Lights should turn off.
- Gradually cover automatic light control sensor. Wait for lights to illuminate. Lights should turn off under any of the following conditions: Light control switch is turned to OFF position. Automatic light control sensor is exposed. Ignition is turned off and driver's door is opened.
- Turn ignition off. Open driver's door (leave it open). Turn light control switch to AUTO position. Cover automatic light control sensor. Ensure lights illuminate when ignition is turned on.
- If operation is as specified, but complaint is headlight illumination is too early or too late, adjustment is required. See «AUTOMATIC LIGHT CONTROL SENSOR»(ref-9018-S40867950762000100200000) under ADJUSTMENTS. If system is inoperative or operation is abnormal, check system circuits and components. See «CIRCUIT TESTS»(ref-9018-S19361603872000100200000) and «COMPONENT TESTS»(ref-9018-S27602429072000100200000) .