Circuit/System Verification
WARNING: This page is about a different car, the 2008 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
Engine ON, press and release the cruise control ON/OFF switch while observing the Cruise On/Off Switch parameter in the ECM data list with a scan tool. The parameter should change and the indicator lamp should turn ON or OFF accordingly each time the switch is actuated.