Daytime Running Lamp: Description and Operation

DAYTIME RUNNING LAMPS
Vehicles manufactured for sale in Canada illuminate the high beam filament at a reduced intensity when the engine is running and the exterior lamps are turned off. This feature is enabled by the Body Control Module (BCM) and a solid state Daytime Running Lamps (DRL) relay, which is installed in the Junction Block (JB). The high beam relay is omitted from the JB on vehicles equipped with DRL.

When the BCM monitors an engine speed signal of greater than 450 rpm and the status of the exterior lighting switch input is Off, the BCM duty cycles the DRL relay to produce illumination of the headlamp high beam filaments at a reduced intensity. The BCM also provides normal headlamp high beam operation through the DRL relay on vehicles so equipped. When the DRL relay is energized, it provides battery voltage from a fused B(+) fuse in the JB to the headlamp high beam filament through the DRL relay output circuit.