The Body Control Module (BCM) controls DRL operation using the ambient light sensor, ignition switch, and parking brake switch inputs. When the ambient light sensor input to the BCM indicates daylight conditions, the ignition is ON, and the parking brake is released the DRL R and DRL L relays are energized. The switch and coil sides of the DRL relays are supplied battery positive voltage through circuit 2740. The BCM energizes the DRL relays by providing ground through the DRL relay control circuits 1966 and 1976. When the DRL relays are energized battery positive voltage through circuit 2740 is supplied to the front turn signal lamp feed circuits 1314 and 1315. The BCM receives inputs from the turn signal switch and the hazard warning switch through the front turn signal monitor circuits 14 and 15. When the BCM receives a voltage signal from the electronic flasher through the left and or the right turn signal monitor circuits, the BCM de-energizes the approiate DRL relay or relays until the turn signal switch has returned to the neutral position or the hazard warning switch is turned off. The de-energized DRL relay or relays allow normal front turn signal or hazard warning lamp operation.

When the ambient light sensor to the BCM indicates low light conditions the DRL R and DRL L relays are de-energized and the ALC HDLP and ALC PK LP relays are energized. The ALC relays are supplied battery positive voltage through the same circuits which supply voltage to the headlamp switch for manual headlamp and parklamp operation. The ALC relays are energized by the BCM by grounding the ALC relay control circuits 999 and 1784. When the ALC relays are energized, battery positive voltage is supplied to the headlamp dimmer switch and parklamp feed circuit bypassing the headlamp and parklamp ON/OFF switches.