i have a 2005 chevy uplander and it has automatic daytime running lights and auto headlights as most gms.auto head lights come on automaticly when turned to the auto position,by means of a sennsor located in the dash when it starts to get dark,doesent always work on cloudy days..day time lights come on in drive always.you could have a bad sensor in the dash that turns on the headlights when it detects darkness,or it could be a faulty light control module.best bet is bring it to a mechanic and have them find your issue.

 

this isn't an uplander. Maybe the higher lines (conversion vans, passenger style, etc) have this feature, but most of these big vans don't have auto lights. You have to manually turn them on. If it is something you must have, DEI makes a kit you can add to make it work that way.