My girlfriend just bought a new to her 2007 Tc and whenever the car is not running and locked, it will randomly flash the parking/brake lights and chirp the horn about 6 times then stop, every so often. We tried shaking the car, walking past it to see if it would trigger it but nothing, it happens mostly from the driveway at nighttime.

I'm not sure how to tell if it had an aftermarket alarm installed in the past that could be causing the issue, it has a stock Scion key fob.

Did some searching and it looks like these cars don't chirp from the factory when the lock or unlock button is pressed on the key fob, which hers does leading me to believe that the previous owner has tinkered around with it a bit?

Thanks