Question Interior alarm?

I just cleaned my injectors had the intake off to repair vacuum lines and replaced the serpentine belt that lasted me 1 season. I started the car and had all kinds of codes and a dash light display for the fourth of July. Turns out I forgot to plug in a electrical connecter on the passenger side of the engine on the valve cover. While dealing with that I discovered a leaking injector. So I fixed that. Now to my question. When I re started the car to test my work everything went fine. I got some codes the usual & 3 other codes under BORFA which I've had for well over a year. I got out to do a visual of the engine while it was running. Satisfied I returned to the interior to shut it down to hear some kind of an alarm that sounded like it was coming from the upper left side of the dash. It sounded like a high pitch squelch but not real loud. It would do a long beep then some shorter ones then some two tone ones then repeat. Everything thing seemed normal except my hood was open. I've heard a variation of this before but it was brief and never went through the whole song before. Any ideas?