2000 Toyota Echo

Last week, my check engine light came on. After I filled my gas tank and drove about 200 miles it went off. It came on again yesterday. I stopped at autozone and the guy there said it was reading a multiple misfire. I took my car to firestone for my oil change and had them run the diagnostic. They told me that my car’s computer would not connect with their machine. Does this generally mean that the computer is in need of repair? or hopefully not replacement? Could it just be a fuse? I have an appointment at at toyota dealer saturday