True North wrote:
My #2 son gave me one a couple Christmas ago.
I've had no use for it driving reliable new Toyotas, but he used it a
number of times on his Dodge Charger and one of his buddies vehicles.
Believe he has to take the error code from the reader and use his
smartphone to access a Site where he enters the code and gets the details.

You get check engine lights on Toyota's also.