Sounds like you've got a burnt-out taillight bulb.
- 1 - go to your local auto parts store and ask them to look up a taillight bulb for your make, model and year, and buy it.
- 2 - Access the tail-light bulb holder by opening up the tail light from *inside* the trunk of the car. (This is trickier than I've written here...but I don't have a Toyota Avalon so I can give exact instructions). This usually involves a flat head screwdriver, a Phillips head screwdriver and a wrench at most for tools. With many tail lights, there are a few screws to undo, or even just clips to unclip from inside the trunk to pull the bulb-holder out of the light housing.
- 3 - Remove the burnt out bulb and insert the new one.
- 4 - Have a friend look to see that your brake light goes off when you stomp on the brake. (Or use a large mirror, angled so you can see it from the driver's seat to do the test yourself.)
If it works, voila! If it doesn't, you've got electrical issues...or bought a burnt out bulb. To test the bulb, you can slip it into the working tail-light housing on the other side and test it...
