Daytime Running Lamp Control Unit: Description and Operation

CIRCUIT OPERATION
On vehicles built for sale in Canada, the headlamps operate, at reduced intensity, when the ignition switch is in the RUN position and the parking brake switch is OPEN.

In the Power Distribution Center (PDC), a bus bar connected to battery voltage feeds circuit A1. In the RUN position, the ignition switch connects circuit A1 to circuit A21. A 30 Amp fuse in the PDC, protects circuits A1 and A21.

Circuit A21 connects to a bus bar in the fuse block. The bus bar in the fuse block feeds circuit G5 through a 5 Amp fuse in cavity 11. Circuit G5 is powered only when the ignition switch is in the RUN position.

Circuit G9 connects to the DRL module. The G9 circuit splices to the brake warning switch, park brake switch and instrument cluster brake warning bulb.

Circuit L20 from the headlamp and dimmer switch supplies battery voltage to the DRL module at all times. Circuit A3 from the PDC feeds circuit L20. A 40 Amp fuse in the PDC protects the A3 circuit.

From the DRL module, circuit L4 powers the LOW beams of the left and right headlamps. The DRL controls the power to circuit L4. Circuit L4 connects to cavity 10 of the Daytime Running Lamp (DRL) module.

Circuit L3 feeds the high beams of the headlamps. When the operator flashes the headlamps with the stalk of the multi-function switch, the DRL senses voltage on circuit L3. When it senses voltage on circuit L3, the DRL module stops supplying power to the low beams on circuit L4.