With Service Lock And & Centering Window
WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Hold SIR coil assembly with rear side facing up. See Figure. While depressing service lock, rotate coil hub in direction indicated by directional arrow until it stops. Rotate coil hub in opposite direction 2 1/2 turns. Release service lock.