The Location of the Flasher Relay on a Toyota Siennaby John Walker
Toyota followed standard design in creating the flasher relay location for the Sienna models. The flasher is mounted high on the firewall behind the dash. You will need to get on your back on the driver's side floor to view and reach the relay. Before replacing the flasher, check the turn signal fuse.
Shine a flashlight angled upward from beneath the dash.
Trace the steering column with the flashlight toward the firewall, and up toward the dash panel.
Remove the relay. The relay is a small black square. A few relays are housed there. The turn-signal relay is the largest of the group. The relay should pull out readily, although it may require some effort. Push the new relay into place. The turn-signal relay can fit into the wiring harness in only one direction, so you cannot install it incorrectly.