I have a 2003 Civic EX. I know it has an immobilizing anti-theft device,
but thought it was quiet. Yesterday, I had parked, and while I was
removing the key and getting out, the horn began sounding, in a pulsating
manner and the lights began flashing on and off.

I put the key back in and the alarms stopped. The car acted completely
normally.

Has this happened to anyone?
Bob

 

Yes, as far as I know putting the key into the ignition resets the
alarm.

-RA