To start this story off.. I didn't even know my 2004 Honda Fit had an alarm at all as I don't have a remote key. Just a key with a H logo black rubber thing with a metal key stick.

So today I decided to lock the door without the key(putting the parking receipt in the window, couldn't be bothered locking with key) came back later and unlocked with key and bam the alarm goes off.

So I'm currently parked in the middle of my city. If I unlock my for the horn beeps but if I shoot in the car with the for locked for about 10 seconds it turns off by itself. If I unlock the for from the inside manually the horns starts beeping.

If have the door unlocked and car started the beeping just doesn't stop.

This is really loud and grabbing a lot of attention
.

Ive only had the car for a couple months so I don't know much about it. The guy I bought it off said it didn't have an alarm so I was baffled when an alarm went off.

 

I'm not sure if you're care came with a factory alarm but it might have had an after market system installed as a dealer option. Bring it to a dealership to have them take a look.

I used to I install alarms for dealerships and this sounds like it might be the cause.. GL