INSPECTION PROCEDURE 5: When the Auto-cruise Control "CANCEL" Switch is Set to ON, Auto-cruise Control is not Cancelled.: Diagnosis
WARNING: This page is about a different car, the 2005 Dodge Stratus and 2005 Chrysler Sebring. However, it is still accessible from the selected car via links, so may be relevant.
Replace the auto-cruise control switch. (Refer to AUTO-CRUISE CONTROL ). Then check the malfunction is eliminated.