Dome light/map lights wont turn on.

[alljuiced3]

2003 gmc sierra 1500... when i open my doors the lights on the bottom of either door turn on but the map lights and dome light wont. When i press the interior light dimmer switch to the on position (all the way up), they wont turn on either. The lights on the doors do... in this position all the interior lights should turn on (map lights and dome light)... the map lights will work if i manually press the buttons on the over head console though. what could possibly be causing this...