I have a 2003 screw and noticed the other day the passengers side mirror turn signal is staying on. So I shut truck off and it was still on in the off position. Don't really know what it is that's making it stay on even when the truck is off. Haha the light is not flashing either just staying on. Sorry don't know how to explain it real well. But Any thoughts ?

 

Sounds like a short in the wires.

 

pop off the mirror cover. Put the mirror all the way down and there are clips. Use a flat head. The check the wires. If they are not bare and touching then if you can check with a volt meter. If it's getting a constant power then you need to chase the wires.