Daytime running lights not working

[stilly]

Contrary to all the posts on daytime running lights, I would like to get these working. 2003 2500HD Duramax/Alllison

One light went out, I changed both bulbs and nothing ever came back on. I have since replaced the bulbs with another set of new bulbs and nothing. I have taken the bulbs back out, put them back in, shook the wire bundles the best I could to see if there was a loose wire- nothing. The fuse looks good, but has not been changed.

What do you recommend next?

[precision37]

This may sound silly, but is your parking brake fully released when you check the lights?

[DmaxMaverick]

The lamps only come on when the E-brake is OFF, Ign. ON, and the gear selector OUT of P. Also, if I install bulbs backwards (rotated 180

[stilly]

I believe a combination of all that did it. I am not sure what specific thing it was. Thanks!