Rep Power: 0

Three times already I’ve parked cut off the car and the horn honked over and over as soon I either pulled the key out the ignition or opened the door. Also once it starts honking, the locks can only be used manually. It seems to stop if I put the key in the door and turn the key. The car does not have an alarm but maybe some sort of built in safety system that it does this. If I put the key back into the ignition it will start but the horn continues to honk. It stops after about 5-10 minutes. I’ve only tried the key in the door once so I’m not sure if the horn stop as a coincidence or not. Anyone having this problem? I have not driven the car while honking. 2009 Honda civic

 
Rep Power: 222

Sounds like an alarm.
check under the dash