Automatic Headlamps

AUTOMATIC HEADLAMPS
The optional automatic headlamp (auto low) system includes the SCM, the FCM, the EMIC, the Electronic Vehicle Information Center (EVIC), the left (lighting) multi-function switch and, depending upon vehicle equipment either the sun load sensor on the top of the instrument panel or the Rain Sensor Module (RSM) on the inside of the windshield below the upper windshield opening header. First, the Auto Low option must be enabled using the customer programmable features function of the EVIC. Then the Auto position must be selected using the left multi-function switch.

Once these prerequisites have been met, the sun load sensor or the RSM provide an ambient light level input to the EMIC. The SCM responds to these inputs by sending the appropriate lighting request messages to the FCM over the CAN data bus. With the engine running, the FCM responds to these messages by automatically controlling a pulse width modulated voltage output to the selected headlamp bulbs through the right and left low beam feed circuits to illuminate the headlamps. The FCM also sends the appropriate electronic messages back to the EMIC to control the illumination of the high beam indicator.