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Toyota Prius Rear Brake Light LED Problem Solution

If you have a generation 2 Toyota Prius with a strange issue with the LED part of the brake light, I may have an easy fix for you.

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Gen 2 Toyota Prius introduced us to a new lighting world that has changed the way we light up our stop lamps.

One of the reasons I enjoy Prius as much as I do is the low cost of maintenance. The LED brake lights are one of the items Prius uses to keep the costs down.

LED lamps have a much longer life span than incandescent bulbs and are much brighter too. But what happens when the lamps fail, or in this case, have a low light output.

The LED lights are not a simple replacement like the others are so, what do you do?

Prius Brake Lamp Issue, Low Light Output.
On my most recent purchase of a 2006 Toyota Prius, I noticed that one of the taillights had a low light output. What comes to my mind when I see issues such as these is high resistance.

The LED part of the lamp is controlled by a circuit board that regulates how the lights function. I had never encountered this issue and was not sure how to diagnose what was faulty. So I did what I could do and test everything to see if I could find the problem.

2007 Toyota Prius Touring Edition

I pulled the LED controller board out and performed a continuity test between all the points. Everything checked out. I traced all the wires and checked each connection carefully. Each end had no issue.

Lastly, I decided to power up the circuit with my power probe to see if I could find a weak spot in the wiring. This is where things got interesting.

At first, when I applied power to the circuit, the lights were still dim, just as they had been on the car when plugged in. I pulled the connectors and checked each one carefully. No corrosion; nothing seemed to be out of place.

I replace the connectors and powered up the circuit one more time, clear as day, and the lights were perfectly bright again.

My best-educated theory is that the pins on the connectors did not have enough contact and therefore could not supply adequate power to the lamps.

This "high resistance" kind of issue would explain the reason for the low light output. After moving the connectors, the contact points could have had very minimal amounts of corrosion, and hooking them back up may have cleaned that off enough to where the power could flow properly again.

My other part of this theory is on Gen 2 Prius; the driver's side rear hatch area is known to leak water sometimes. While there was no watermark anywhere on the tail lamp housing that I could see, excess moisture could have built up in the connector and caused corrosion to inhibit electron flow.

Any way you look at it, the issue with the lower power output on the LED circuit of the tail lights is now solved, and it functions as designed.

If your Toyota Prius LED tail lamp part of the brake light assembly is dim, I suggest taking it apart and checking all the connections. It worked for me, and I hope that it can work for you too.

Thank you so much for reading. Remember, Today's Adventure is Tomorrow's Story. I will see you in the following article.

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Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter can be reached on Linkedin and you can tweet him at The_hybrid_guy on Twitter. Find his page on Facebook at Certified Auto Consulting. Read more of Peter's stories at Toyota news coverage on Torque News. Search Toyota Prius Torque News for more in depth Prius coverage from our reporter.

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CatLadyofTroy (not verified)    May 26, 2021 - 3:44PM

My rear right brake light on my 05 Prius, I thought, was burned out, but rechecking it, it was working but very dim. I was at Toyota a couple months ago and they said I needed a new brake light assembly ($400). They were out of stock so I didn't get it. Now my inspection is due. Will it pass with a dim brake light? Or, can you recommend a mechanic I can take it to, to do as you say, check the wires and clean the connectors. I really don't have the money to replace the assembly. Any comments are appreciated.