daytime running lights don't turn on on 2002 GMC Sierra 2500 HD

Well, the other day I decided to replace both bulbs for my daytime running lights (they have been burned out for 3 years) with new bulbs, but they won't turn on. I noticed that the plastic piece looked like it had got hot because it is somewhat black. I checked all the fuses under the hood and in the cab and still no lights. Anyone have any suggestions.

Asked by for the 2002 GMC Sierra 2500 HD
check for power to the bulb sockets, the black color is a indicator that the bulbs are not fitting tight in the sockets and are getting hot from arcing. It may have damaged the wires close to the bulbs and or the sockets themselves.
Thanks for your help, however I figured out what the problem was. To check to see if the lights were on I'd set the parking brake and put it in drive. Come to find out the lights are not suppose to come on when the parking brake is applied. thanks.
Will they not work when it's in park?