There are three different situations that will trigger the alarm system on your Hyundai Sonata. If someone opens any of the doors but does not use the remote control or Sonata key to do so, the alarm will sound. Also, if you open the trunk or hood without unlocking the car with the remote control or the key, the alarm will also go off. You will need to disable the alarm to prevent the horn from sounding while the turn signals are flashing. The lights and sounds will continue for 27 seconds, then the process will repeat.