Lets start by checking voltage at the DRL relay in the under hood electrical center.If the voltage is good ,try switching relays with another or substitute a known good one.If this checks good the next step you will need the use of a scan tool to view the data from the Body Control Module.First check to see if there are any failure codes pertaining to DRL,then view data for input sensors.I see you said the e-brake was off ,but make sure that is what the computer (BCM) is seeing also.Look at the data for the light sensor& BCM control of the DRL.Here is a description of circuit operation which may help you.
The ambient light sensor is a light sensitive transistor that varies its voltage signal to the body control module (BCM) in response to changes to the outside (ambient) light level. When the BCM receives this signal it will either turn on the daytime running lamps (DRL) or the headlight relay for auto headlamp operation. Any function or condition that turns on the headlights will cancel the daytime running lamps operation. The daytime running lamps (DRL) separate lamps independent of the headlamps. With the headlight switch in the OFF position, the DRL will either be turned ON or OFF, after an approximate 8 second delay depending on whether daylight or low light conditions are sensed. The DRL 10 A fuse in the engine wiring harness junction block supplies battery positive voltage to the daytime running lamp (DRL) relay switch contacts. The IGNE 10A fuse in the engine wiring harness junction block supplies ignition positive voltage to the DRL relay coil. When the BCM energizes the DRL relay in daylight conditions, the current flow is to both DRL lamps and to ground G100. The DRL will operate when the ignition switch is in the RUN position, the gear selector is not in the PARK position and the parking brake is released. When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate.
The automatic lamp control (ALC) system and the DRL feature can be temporarily disabled by performing the following procedure:
Note: The ALC and DRL cannot be turned off on the Canadian vehicles.
- Turn the ignition to RUN.
- Press the DOME OVERRIDE button four times within six seconds.
A chime will sound informing you that the system is off. The system will remain disabled until the ignition is cycled off and then on or by pressing the DOME OVERRIDE button four more times within six seconds. The chime will sound again signaling that the system has been reactivated.