DRL stands for Daytime Running Light which originally was developed and used in countries that are more prone to foggy conditions and it is a safety feature which has now become standardized by many car manufacturers. In some countries, it is by law required features (such as Canada). Please note that the DRL feature is not site specific on a vehicle. As long as the supposed “DRL” Light remains on during the day (with the Parking Brake disengaged) and turns off OR becomes dimmer (automatically) when the “Parking Light” Light is engaged, then the supposed light should be your DRL.
There are two main types of Day-time Running Lights Halogen DRL vs. LED DRL. There are other types of DRL, however to keep things simple, we will focus on the two main types. The picture example above shows the different projections between LED and Halogen.
DRL may use your low beam or high beam or others, but it is normally supplied only with 27.5W power versus the original 55W halogen bulbs used in the halogen low beam or halogen high beam. So it might create an issue if you upgrade a genuine xenon HID system to the headlight if the DRL function is using the new xenon HID system. This is because standard xenon HID needs 35W to power it, while DRL is only supplied with 27.5W, it means the system is underpowered. Flickering, error message, not able to fire it up would be the common issue if you have DRL powering the HID system. To solve it, the installer can either disable the DRL feature altogether or do minor re-wiring so the DRL is powering something else other than the new HID light.