Toyota OBD-II Port Locations
The standard spot
Every 1996-and-newer Toyota, Lexus, and Scion has the same 16-pin DLC3 connector. By federal law it has to be within two feet of the steering wheel, so it lands under the dash on the driver side. Feel left of the steering column, just above the lower dash edge. Camry, Corolla, RAV4, Tacoma, Tundra, Prius, Sienna, Highlander. Same area on all of them.
When it hides
The connector is not always in plain sight. It can sit further left or higher under the dash. Feel along the lower edge and look up under the dash before you give up.
Pre-1996 Toyotas
Older Toyotas use a diagnostic connector under the hood near a fender, or under the dash on the driver side. Jump terminals TE1 and E1 with a paperclip, key on, engine off. Count the check-engine flashes. That system is OBD-I, a different language from everything on this site.
Scanner will not connect
Check the port for bent pins first. Then check fuses. The port needs battery power to run the scanner, so a blown fuse kills the connection. Fix it and the scanner connects.