Hello and thank you for your post. I am a master certified GM tech, with 15 years Saturn experience,and can help you to resolve your issue.
teh sensor is located under the dark colored dome on the dash. Passenger side.
It is the ambient light sensor. It decides whether the daytime running lights or the automatic headlamps should be on.
If the sensor is OK then you may also have a bad resistor for the drl lights.
IT is located under the drivers headlamp assembly. It is a white porcelin component about 2-3 inches by 1 inch and has a connector mounted directly to it. The other one with the 2 wires coming from it is for the fans.
if you suspect the resistor is bad, unplug it and jump it and see if the drls work then. If they do then the resistor is no good.
Is this the sensor that automatically turns the driving lights on when the motor is started? I realize there is a link with the emercency brake. Our vehicle is not equipped with a sensor to turn the lights on or off. We just use the manual switch. I m just concerned about finding the module that operates the daytime running lights and knowing how to test it. Thanks.