Automatic Headlamp Operation

WARNING: This page is about a different car, the 2011 Jaguar XKR, 2011 Jaguar XK, 2010 Jaguar XKR, and 2010 Jaguar XK. However, it is still accessible from the selected car via links, so may be relevant.

The automatic headlamp function is a driver assistance system. The driver can override the system operation by selection of side lamp or headlamp on if the ambient light conditions require front and rear lighting to be active. The automatic headlamp system uses a light sensor and the AJB, which is connected to the instrument cluster, via the medium speed controller area network (CAN) bus, to control 'AUTO' headlamp functionality.

The light sensor is located in the center of the instrument panel upper surface. The sensor has three functions; houses the alarm system light emitting diode (LED), auto lamp function for AUTO headlamps and sun load sensor for the air conditioning (A/C) system.

The sensor is hardwired to the instrument cluster which supplies a 5V current via a pull-up resistor to 2 photodiode light sensors within the sensor housing. The ambient light signals are returned to the instrument cluster by the light sensor varying the current drawn from the 5V output, hence varying the voltage at the 'pull-up' resistor. The instrument cluster then outputs a message relating to the ambient light level on the medium speed controller area network (CAN) bus. The AJB receives the message and determines if AUTO lamps are required to be activated.

Operation of the 'AUTO' headlamps requires the ignition to be in the ignition mode and the lighting control switch must be in the AUTO position. The AJB will only activate the AUTO headlamps on receipt of a valid ambient light signal on the medium speed controller area network (CAN) bus from the instrument cluster.