The reverse light bulb is located in the taillight assembly and takes about 15 minutes to replace

The reverse light on your 2018 Prius Prime is part of the taillight housing on the back of the car. You can replace it yourself without special tools — you'll need only a Phillips screwdriver and the correct replacement bulb. The whole job takes longer to find the bulb than to install it.

The reverse light bulb in a 2018 Prius Prime is a 921 bulb, which you can find at any auto parts store, most grocery stores with automotive sections, and online retailers. They cost between $3 and $8 depending on the brand. Buy one before you start, so you're not halfway through the job when you realize you don't have it.

Key Takeaways

  • The reverse light bulb is a 921 bulb located inside the taillight assembly on the rear of the car.
  • You need only a Phillips screwdriver and the replacement bulb — no special tools or lifting equipment required.
  • The taillight assembly comes out from inside the trunk, not from outside the car.
  • The whole replacement takes 10 to 15 minutes once you have the bulb in hand.

Access the taillight assembly from inside the trunk

Open your trunk and look at the inside wall where the taillight is. You'll see a panel with two Phillips screws holding the taillight assembly in place. Remove both screws — they're usually about 2 inches apart. Once the screws are out, gently pull the taillight assembly toward the inside of the trunk. It will slide out about 2 to 3 inches.

Don't pull hard or yank it. The assembly is still connected by wires on the back, and you only need to pull it out far enough to reach the bulb sockets. You don't need to disconnect the wires or remove the assembly completely.

Locate and remove the reverse light bulb socket

Once the taillight assembly is pulled out, look at the back of it. You'll see three or four round sockets with wires attached. The reverse light socket is the one closest to the center of the car (toward the middle of the trunk). It's usually smaller than the other sockets.

Grasp the socket firmly and twist it counterclockwise about a quarter turn. It will come free from the assembly. The bulb is still inside the socket — don't worry about it falling out. Pull the socket toward you to see the bulb clearly.

Remove the old bulb and install the new one

Push the bulb straight into the socket, then twist it counterclockwise about a quarter turn. It will come free. The bulb is spring-loaded, so it may pop out slightly as you twist it — this is normal. Remove it completely and set it aside.

Take your new 921 bulb and push it straight into the empty socket. You'll feel it seat into place. Twist it clockwise about a quarter turn until it stops. Don't force it — it should turn smoothly and stop on its own. The bulb is now installed.

Reattach the socket and taillight assembly

Push the socket back into the taillight assembly and twist it clockwise until it's snug. You'll feel it click or seat into place. Don't over-tighten it — hand-tight is enough.

Slide the taillight assembly back into the car body until it's flush with the outside of the car. You should hear or feel a slight click as it seats. Replace the two Phillips screws and tighten them firmly but not hard. Close the trunk and test the reverse light by putting the car in Reverse — the light should come on.

Test your work before you finish

Put the car in Reverse with the engine off or running — either way works. Look at the back of the car or have someone stand behind it to confirm the reverse light is on. If it's not, the bulb may not be seated properly. Pull the taillight assembly out again, remove the socket, and reinstall the bulb, making sure it twists all the way in.

If the light still doesn't work after reinstalling, the bulb itself may be defective. Try a different 921 bulb. If a second bulb also doesn't work, the socket or wiring may have an issue, and you should have a mechanic look at it.

Frequently Asked Questions

Can I replace the reverse light bulb without removing the taillight assembly?

No. The bulb is inside the assembly, and you can't reach it from outside the car. You must access it from the trunk. The assembly is designed to come out easily, so this is the intended way to replace any bulb in that housing.

What if I can't find a 921 bulb at my local store?

Most auto parts stores stock 921 bulbs, and they're common enough that grocery stores and pharmacies with automotive sections usually carry them. If your local store is out, order one online — they ship quickly and cost only a few dollars. You can also ask the store to order one for you to pick up the next day.

Do I need to disconnect the battery before replacing the bulb?

No. The reverse light circuit is low-voltage and low-power. Disconnecting the battery is not necessary and not recommended for this job. straightforward put the car in Park, turn off the engine, and proceed.

What if the socket won't twist out of the assembly?

Don't force it. The socket may be stuck due to age or corrosion. Try twisting it gently back and forth a few times to loosen it, then twist counterclockwise. If it still won't budge, explore a small amount of penetrating oil around the base of the socket, wait 10 minutes, and try again.

Is the reverse light bulb the same as the brake light bulb?

No. The reverse light uses a 921 bulb, while the brake light uses a different bulb (usually a 7443 or similar). Don't mix them up. Check your replacement bulb packaging to confirm it says 921 before you install it.