I just purchased a 2001 Duramax 2500, with 64 K miles. My question is one that may be hard to answer. The truck has a toggle switch down next to the parking brake release, since this is a used truck I am not sure what it is. Any thoughts of what it could be? The dealer had no idea, and thought it appeared after-market.

Congrats on the new truck. Probably a Hi Idle switch for the cold months.

Trace the wires and find out.

I tried to trace the wires but they just go into a box right behind the dash right behind it. I may find out who traded it in and see if I can get their number. Also, when did they stop making the 6.5 L. My 2001 is a 6.6, was this the first year of this?

Valet switch for aftermarket alarm system????

I didn't think about that. I am just leaving it in the off position for now.