Pinpoint Test C: DTC P0579 or P0581 - Speed Control Switch Circuit Failure: Notes
WARNING: This page is about a different car, the 2008 Mercury Sable, 2008 Ford Taurus X, and 2008 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.
Refer to appropriate SYSTEM WIRING DIAGRAMS article, Speed Control for schematic and connector information.