What you need to know before you start

The 2018 Prius Prime has two reverse lights, one on each side of the rear bumper. You can replace either bulb without removing the entire taillight assembly — the bulb socket twists out from inside the trunk. The whole job takes about 10 minutes per side, and you need only a replacement bulb and possibly a small flathead screwdriver.

Toyota uses a 921 bulb for the reverse lights on the 2018 Prius Prime. This is a single-filament, white bulb rated for 12 volts and 27 watts. You can buy one at any auto parts store, Walmart, or online for $3 to $8. Have a replacement on hand before you start, because you'll need to test the light before you close everything up.

Key Takeaways

  • The 2018 Prius Prime reverse lights use 921 bulbs, which you can access from inside the trunk without removing the taillight housing.
  • You twist the bulb socket counterclockwise to remove it, then pull the old bulb straight out and push the new one in until it clicks.
  • Test the reverse light by putting the car in Reverse before you close the trunk, so you know the bulb is working.
  • If the new bulb doesn't light up, the socket itself may be damaged or there may be a wiring issue that requires a mechanic.

Access the bulb socket from inside the trunk

Open your trunk and look at the inner wall on the side where the reverse light is out. You'll see the back of the taillight assembly. On the 2018 Prius Prime, the reverse light socket is located toward the outer edge of the taillight area, closer to the side of the car than the center.

You may see a rubber access panel or a small opening in the trunk lining. If there's a panel, peel it back gently. If there's no panel, you're looking directly at the socket. Reach in and locate the bulb socket — it's a cylindrical piece about 2 inches long that sticks out from the back of the taillight housing.

Remove the old bulb and socket

Grip the bulb socket firmly and twist it counterclockwise. It will turn about a quarter turn before it stops and comes free. Don't pull hard — let the twisting motion do the work. Once the socket is out, you'll see the bulb seated inside it.

Pull the bulb straight out of the socket. It should come free with gentle pressure; don't twist it. Set the old bulb aside. Look inside the socket to make sure it's clean and dry. If you see corrosion or moisture, wipe it out gently with a dry cloth before installing the new bulb.

Install the new 921 bulb

Take your new 921 bulb and push it straight into the socket. You'll feel it seat with a click when it's fully inserted. Don't twist the bulb — just push it in straight. The bulb should sit flush with the socket opening.

Now twist the socket clockwise to reinstall it into the taillight housing. Turn it until you feel it stop — you'll know it's seated correctly when it won't turn any further. Don't force it; the socket should seat smoothly with light pressure.

Test the reverse light before closing the trunk

Before you close the trunk, test the light. Have someone sit in the driver's seat and put the car in Reverse, or use your key fob to unlock the car and manually shift it into Reverse if you're alone. Look at the reverse light you just replaced — it should glow white and bright.

If the light works, close the trunk and you're done. If the light doesn't come on, shift back to Park, open the trunk, and check that the bulb is fully seated in the socket. Twist the socket to make sure it's fully installed. If it still doesn't work after you've reseated everything, the socket or wiring may be damaged and you'll need a mechanic to diagnose it.

Repeat for the other side if needed

If both reverse lights are out, follow the same steps on the other side of the car. The process is identical — access from the trunk, twist out the socket, pull the bulb, push in the new one, and twist the socket back in.

If only one light is out and the other is working, you only need to replace the one that's burned out. Reverse lights on the 2018 Prius Prime are independent circuits, so one failing doesn't affect the other.

Frequently Asked Questions

Can I replace the reverse light bulb without going into the trunk?

No. The 2018 Prius Prime reverse light socket is only accessible from inside the trunk. You cannot reach it from outside the car or from the interior cabin. You must open the trunk to access the socket.

What if the bulb socket is stuck and won't twist out?

explore gentle, steady pressure as you turn it counterclockwise. If it's stuck, try wrapping a rubber band around the socket to improve your grip. If it still won't budge after a few attempts, stop and take the car to a mechanic — forcing it can crack the socket or damage the taillight housing.

Is the 921 bulb the same as other bulbs I might have at home?

No. The 921 is a specific size and type. Don't substitute a 912, 920, or any other number — they won't fit or may not work correctly. Buy the correct 921 bulb for the 2018 Prius Prime reverse lights.

Do I need to remove the taillight assembly to replace the reverse bulb?

No. The reverse light socket twists out from inside the trunk without removing the entire taillight. Removing the assembly is unnecessary and takes much longer.