High Intensity Discharge (HID) Low Beam Headlamps (uplevel): Notes

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

Battery voltage is applied at all times to the coil and switched side of the low beam relay. Ground is applied at all times from G200 to the turn signal/multifunction switch. When the turn signal/multifunction switch is placed in the HEAD position, ground is applied from the turn signal/multifunction switch through the headlamps ON signal circuit to the body control module (BCM). The BCM applies ground to the headlamp low beam relay control circuit. This energizes the low beam relay coil, closing the switch side contacts, and applies battery voltage to the LEFT and RIGHT LOW BEAM fuses. Battery voltage is then applied from the fuses, through the low beam voltage supply circuits to the left and right headlamp ballast located in each headlamp assembly. When battery voltage is applied to the headlamp ballast through the low beam voltage supply circuits, the ballast charge the starter to start the lamp. High intensity discharge (HID) headlamps do not have filaments like traditional bulbs, instead the starter uses a high voltage transformer to convert the input voltage into a higher voltage. This increased voltage is used in order to create an arc between the electrodes in the bulb. Ground for the left headlamp is provided at G101 and the right headlamp at G102.