Here is an extract from the PA46 Malibu Pilots Operating Handbook.
2.34 ICING INFORMATION "WARNING" Severe icing may result from environmental conditions outside of those for which the airplane is certified. Flight in freezing rain, freezing drizzle, or mixed icing conditions (supercooled liquid water and ice crystals) may result in ice build-up on protected surfaces exceeding the capability of the ice protection system, or may result in ice forming aft of the protected surfaces. This ice may not be shed using the ice protection systems, and may seriously degrade the performance and controllability of the airplane. During flight, severe icing conditions that exceed those for which the airplane is certificated shall be determined by the following visual cues. If one or more of these visual cues exists, immediately request priority handling from Air Traffic Control to facilitate a route or an altitude change to exit the icing conditions. Unusually extensive ice accumulation on the airframe and windshield in areas not normally observed to collect ice. Accumulation of ice on the upper surface of the wing, aft of the protected area. Accumulation of ice on the engine nacelles and propeller spinners farther aft than normally observed. Since the autopilot, when installed and operating, may mask tactile cues that indicate adverse changes in handling characteristics, use of the autopilot is prohibited when any of the visual cues specified above exist, or when unusual lateral trim requirements or autopilot trim warnings are encountered while the airplane is in icing conditions. All wing icing inspection lights must be operative prior to flight into known or forecast icing conditions at night.
May be of interest to a previous post about auto pilot malfunction. AS the above reminds us more to the point is pilot`s knowledge about the use and limitations of the auto pilot.