Left rear tail light - 2007 Toyota 4Runner

My guess is one of those lamps is burned out, therefore not sending current to the next. My second guess is that the license plate light is last in line, so I would start with the left tail light

check for ground/power on that side for the rear light assemblies.

1) Open trunk
2) Remove small round plastic access panel with a flat tip screw driver by prying open
3) Remove flat tip screw holding tail light assembly
4) Remove tail light assembly by pulling outward, careful not to break plastic guide/nub
5) Disconnect wiring connectors
6) Remove plastic housing access plate on back of tail light assembly by twisting/turning tabs until they click and then lift access plate from tail light assembly
7) When viewing the the bulbs, the turn signal bulb is the bottom left bulb
8) Install in reverse order, ensuring tail light seal seats properly during installation

You need the tail lamp assembly,

Replace bulb

first of all check and confirm whether in the fuse box separates the left from right side and see for blown fuse. or check for any disconnection on the rear light

at the tail lights the wire is blue, at the rear light junction block ( under the rear body about the center of the rear bumper ) the right side tail light wire is brown/white the left side tail light wire is brown, from the junction block to the tail lights both wires are blue.

tail light is seperate filament inside the brake light bulb- change bulb

Blinker too fast, the same side blinker light bulb on the front (or back) is burned. Check the fuses for the rear lights. You might have a light bulb filament stuck.

There was a recall on this, take to the dealer and they will replace the whole socket on this.