Automatic Light Control

WARNING: This page is about a different car, the 2003 Lexus RX 300 and 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.

When the light control switch is set at AUTO, the automatic light control system automatically turns on or off the taillights and headlights depending on the brightness around the vehicle.

The automatic light control sensor converts the intensity of the illumination into frequency and inputs it to the body ECU. When the light control switch is set at AUTO, the signal is input to connector B6 terminal No. 4 (A) of the body ECU. See WIRING DIAGRAMS . Through communication control of the body ECU and door ECU etc., the taillights and headlights are automatically turned on or off.

Turn On Function - When the body ECU receives a frequency signal from the automatic light control sensor, and determines that the brightness around the vehicle is below a predetermined level, it controls the connector B8 terminal No. 7 (TRLY) and connector B5 terminal No. 12 (HRLY) of the body ECU. See WIRING DIAGRAMS . This turns on the taillight relay and HEAD LAMP relay, and thus turns on the headlights and taillights.
Turn Off Function - When the body ECU receives a frequency signal from the automatic light control sensor, and determines that the brightness around the vehicle is above a predetermined level, it controls the connector B8 terminal No. 7 (TRLY) and connector B5 terminal No. 12 (HRLY) of the body ECU. See WIRING DIAGRAMS . This turns off the taillight relay and HEAD LAMP relay, and thus turns off the headlights and taillights. In addition, the headlights and taillights will be turned off when the ignition switch is turned from on to off and the driver door is opened, during automatic light control.