"Hol látod az autót? = "where do you see the car?"
"Hol látsz autót?" = "where do you see a car?"
Hungarian sometimes likes to drop the indefinite article, especially when we're asking for where things are. "Hol látsz egy autót?" doesn't feel right at all. So when you're asking for where one exact thing is, you have to leave that egy. Hope this helps.