Diagnostic Aids
WARNING: This page is about a different car, the 2003 GMC Sierra and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
If the drive belt repeatedly falls off the accessory drive belt pulley(s), this may be caused by a pulley misalignment.
An extra load that is quickly applied or released by an accessory drive component may also cause the drive belt to fall off. Verify that the accessory drive component(s) are operating properly.
If the drive belt is the incorrect length, the drive belt tensioner may not maintain the proper tension on the drive belt.