I have got a problem with lights the overhead dome lights stay on so have removed bulbs and have now noticed as dark evenings the foot lights are staying on all the time whilst driving then they stay on until the 20 min battery saver kicks in.
Have tried the switch in and out by lights and makes no difference.
If left for a day without using then the battery is dead.
I have read about the onstar draining battery and to remove the fuse so shall also try this. Have checked all door switches and they seem fine.
any ideas very much appreciated.

 

DOOR PIN SWITCHES!
Replace the bad door pin switch.
Buy a new one or 2 (always good to have a spare and they are cheap) and install it on the rear door first.
If that does not change things, try the next door, then the next, then the next until you get the lights to turn off when the doors are shut.

Hope this helps