PTO Solenoid
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The solenoid is an upfitter supplied part and is replaceable on most PTOs. The PTO solenoid is used on clutch activated PTOs. The PTO relay supplies the solenoid with voltage when the relay is energized.