Where is the blower resistor on a 2001 GMC crew cab?

The blower motor resistor on a 2001 GMC Sierra Crew Cab (assuming you mean Sierra, as there's no GMC Crew Cab model designation) is typically located behind the glove box. You'll likely need to remove the glove box to access it.

However, the exact location *could* vary slightly depending on the specific trim level and options. It's always best to consult a repair manual specific to your vehicle's year, make, and model for the most accurate location. A Haynes or Chilton manual would be helpful. You can also search online for "2001 GMC Sierra blower motor resistor location" along with your specific trim level (e.g., SLE, SLT, etc.) for more targeted results and potentially pictures from others who have performed this repair.