'Joystick Joystick' alert

From where does the ‘Joystick Joystick’ alert arise when flying Cessna 172, Glass cockpit flying an approach. Can anybody point me to documentation that explicitly explains the criteria. Ive looked in the G1000 pdf. I also have the terrain warning.

That’s not the G1000. You have Mod or something making that sound. Remove all Mods and try again, if silent, you know for sure.