Ohio is different. It has to be your residence or car and you have to be occupying it. Sucks like CA. If you are out and come home to see someone robbing your house, you cant go in and confront them. You cant shoot them as they exit. You cant shoot them if they are carting off your big screen TV. You can shoot at them as they drive away in your 60K SUV. Now if they try to run you over in the SUV, then all bets are off...
According to this Ohio lawyer, you are right, or at least you were right as of 2013.
https://www.thelawofficeofbrianjones.com/blog/2013/02/intruders-and-the-castle-doctrine-in-ohio/
According to info at the link, to be covered under Ohio's Castle Doctrine, a dwelling must be designed to be occupied at night. That does not describe most garages, attached or unattached.