Car won't turn off after installing aftermarket head unit

I would guess that there is some kind of connection between the always on 12V line and the switched 12V line that causes power to be fed to the car. Try unplugging the new head unit and see what happens.

 

You may not have mixed them up, per a wiring diagram, but maybe the wiring diagram is wrong. My suggestion is to use a multimeter and check line voltage on all the wires with the ignition on and off. I'll bet your switched wire is mistakenly labeled and is actually a constant +12. Plan B, you could run a new switched wire from a known source that does turn off - the power feed to the cigarette lighter for instance.

Lastly I've heard of circumstances where a large capacitor fed the stereo and amps after power was off. Do you have that equipment in the system too?

 

After installing the same after market radio system im having a very similar problem. The jvc radio wasn't shutting off on its own, so I manually shut it off. The car then beeped at me as I try to leave and wouldn't lock. When I went back to the prius the next morning the battery was dead.

It seems that the prius power system will not shut off fully after the new radio installation.
Has anyone solved this issue? Can I reset the computer somehow to work with the new radio system?

 

Did you ever solve this? My 2011 with my pioneer is having the exact same issue.