My '03 Silverado has a failing door switch, as sometimes it doesn't register the door as being shut even after several slams. I looked for the switch but couldn't find it! Does anybody know where the switch is on the extended cab, driver's door?

not to sound silly, but it has to be somewhere on the perimeter of the door. Did you check up near the hinges?

Yes. Lol I definitely checked the whole perimeter of the door. Even had the door apart when I replaced the upper door hinge. That was a fun project. I'm guessing that the switch is actually related to the sliding piece of metal that provides the stops for the door between the two door hinges. My haynes manual is completely useless, so I'm hoping someone either has a factory service manual or has had the same switch replaced themselves. Hopefully someone has!

from what i can see it is located in the latch mechanism of the door itself.

That's the second possibility. Unfortunately I really don't feel like pulling the door apart to fix it... But since I'm OCD on maintenance I'm sure I will. I will call the dealer tomorrow and price it. Otherwise I'll go to the trusty ol' junkyard. Unless someone happens to have one laying around...

Maybe I should just keep telling my truck the door is a door, not a jar...?

:lol2:Maybe I should just keep telling my truck the door is a door, not a jar...?:hehe:I notice that there is a switch on the third door handle just under the latch but I have no idea what it is.

The AMP Research PowerSteps use the door open/closed switch or senor whatever it is. I don't know if this attachment will help, but maybe it'll show you something you may have missed.
Maybe if you follow the wires the steps hook up to it'll get you to the switch.

I'll check out that switch under the door handle, and definitely look at that pdf shortly...

I'm gonna sound like an NFL referee here: "Upon further review, it appears as though the door open switch resides within the driver's door." This comes after reviewing the diagram courtesy of rance. The logical solution is that the latching mechanism itself houses the switch.