Horn stopped working which prevented notice to other car at stop backing up, resulting in a crash. Vehicle started turning itself on in accessory mode, flashing lights, disabling keyless entry and starting the vehicle and smelled of an electrical fire, was unable to disconnect battery due to unpredictable turning on and off at vehicles will. Brought vehicle to dealer who confirmed that it was a bad smart entry main control unit module which caused the horn to stop working and the vehicle to turn itself on.