Dim Led Brake Lights On Prius

[IABA11]

PRIUS 2005 6 LED brake light unit:-

For the past 2 years the rear near-side brake light comprising 6 individual LEDs has been dim, but would intermittently become bright again to match the off side one.
This intermittent failure and re-correction indicated a poor connection somewhere within the wiring system but it was uncertain if this was a poor earth connection.

It was corrected by the Toyota Garage in Bristol by removing the boot trim and disconnecting and reconnecting the white plastic multi-wire connector which comprises male and female components.

The Toyota repair lasted for 2-3 months and then failed again. I investigated the white plastic connector myself by disconnecting the plastic male-female plug components. By very slightly twisting each of the 6 blade-like pin terminals with a pair of snipe nosed pliers it was possible to improve the connection contacts within the plug when reassembled. The brake lights instantly became bright again.

The female & male components of the connector can be pulled apart by pressing down the projecting end of the plastic arm which lifts a small latch on the underside of the other end of the arm.

REMOVE COVER TO REVEAL TAIL LIGHT

PULL OUT PLASTIC CONNECTOR AND SEPARATE

(Disconnect male & female parts of plug by pressing the left hand end of plastic bar above – then pull apart.

6 FLAT METAL BLADE PINS

[Maui Prius]

This just started happening to my 2004 Prius. I was searching on-line and saw your post. I will give it a try. I have fixed all kinds of things thanks to posts like this. Thank you! Has your brake light remained bright since?

[IABA11]

Regrettably this fix did not permanently cure the problem and a few days later the brake leds became dull again.

It has still continued to become bright intermitently so I have again tackled the problem by using Halford's Electrical Contact Cleaner which I have sprayed into each half of the connector. I have also used a pair of serrated tweezers to scour the surfaces of the 6 tiny spade terminals in the male part of the connector. So far this has resurrected the brightness again - they both match in intensity.

I have not been overly enamored with the attitude of the Toyota Dealer who has again suggested I replace the entire light unit!

It was suggested that the unit had condensation inside it but it is a sealed unit where the LEDs are and I have inspected it with a strong torch light and can see no water vapour at all.

[Maui Prius]

OK... this is strange... I went to clean the connector and discovered that my rear driver side LED break lights are only wired for 5 not 6 lights... when they illuminate there are only 5. What is up with that. Did Toyota give me a factory second or something... really... not good Toyota... not good...

The intensity of the 5 lights are now equal to the other side... well minus the one light of course.... I mean seriously... has this happened to anyone else? It isn't that there is a burnt out light... it just isn't there... at all.

[Maui Prius]

Well... trust me you can clearly see when you separate the connector to clean it that there are only five of the prongs (blade pins) and one empty socket... pretty clear and simple. Not to mention when the brake is pressed you can see that the bottom right corner area of the brake light the on of the reflector squares is not illuminated. It is not a difficult or tricky thing to diagnose. Not to mention if you count the wires coming into the connector from the LED there are only five... not six.

[nhbari]

I have a 2005 Prius and have recently been experiencing the same symptoms as well, and getting the same response from the dealer that has been servicing my car for nine years. Very frustrating for sure! How replacing a complete light assembly is going to cure a cluster of dim bulbs is beyond me. This looks and acts like an intermittent brown out...not enough current being consistently delivered to the lamps. (It only happens to the break lights on the driver's side.)

On a whim I stopped into a different dealer to see if they had any experience with this problem. At first I got the party line: "We will have to run a complete diagnostic on the wiring from the brake pedal back to the tail light assembly to see if we can find the problem. If we can't find anything you'll probably have to replace the complete assembly."

But then the service manager suggested that the next time it happened try opening and closing the hatchback and see if it cleared up. Since all the wiring for the tail lights runs through two rubber sleeves at the top of the hatchback, between the hinges, they are flexed every time the door is opened. If I noticed a change that could help narrow down the search for the problem. At least he was thinking outside the corporate manual!

And that is exactly what happened today. The brake lights were dim when I left to run errands and after opening and closing the hatchback a few times while out and about the bulbs were fully illuminated when I got home. So, he may be onto something and perhaps the problem is upstream from the light assembly. I intend to pursue it further with this guy. Stay tuned.

[Grumpy Cabbie]

Does WD40 sprayed on the connectors help?

[ThruSST]

Pulling an old thread back to the top .....

Is there a confirmed fix to this dim brake light issue? I've had the rear lamp out of the wifes car but no bad connections to be seen. I'll try to tighten the connections on the pins but surely it would get gradually dimmer instead of going to a particular brightness wouldn't it?

[Raul2828]

I have the same problem with my  prius  is it easy  try to fix it self but or bring it to a dealer 

[victortran]

It really simple and true. I just tried and it works on my prius 04. Thanks a ton  for your guide, IABA11!

[Michael Arthur]

Yay had the same problem left side brake light dim $2oo NZ dollars for a 2nd hand light gave the plug a wiggle and bobs your uncle full brightness again your feed back just saved me some ghost bucks. Thanks :) 

[MitchKing]

I just ran into the same problem with the right-side brake light assembly on my 2005 Prius.  After disconnecting the quick disconnect connector, I see six SOCKETS for terminal ends, but only five actual terminal ends, so my assumption is that at least some 2005 models come with only five LED units per brake light assembly.  I didn't see any evidence of corrosion on the terminal ends, so I gave the male ends a slight twist with a pair of needle-nose pliers--like another previous poster did--but doing so did not make my right-side assembly any brighter.  

As my wife held the brake pedal down, I tested the terminal ends with a volt meter and discovered that only one of the female sockets—the one with blue insulation--had 12 volts on it; the other four female sockets…and all five male terminal ends…were not showing any voltage at all (and thus were not carrying any amperage).  The left side brake assembly was working just fine, so I checked its quick disconnect connector using a volt meter the same way and got the same results as I had with the volt meter test on the right side: the female socket supplied by the blue insulated wire was the only “hot” one when the brake pedal was depressed—so I’ve assumed that there’s nothing wrong with the wire harness up to the male end of the right side brake assembly and the problem probably lies in the brake assembly itself. 

I’m on vacation and I’m not sure how electricity from the blue wire gets distributed to the other four wires and LEDs in the assembly, so when I get back home…and if I have the time…I’ll try taking the assembly apart to see if whatever is wrong is something I can fix without buying an entire brake light assembly.  In the meantime, I thought I’d add my information: 1) about the number of wires in my quick disconnect connector; and 2) that, under normal operation, the female terminal supplied by the blue insulated wire appears to be the only terminal that has 12 Volts on it when the brake pedal is depressed. 

[ntulsian]

I cut open the back off the light using a Dremel tool on the top portion of the black plastic.

this gave me access to the three sections of LEDs that are screwed in. Once I unscrewed and took the three sections out I was able to check which of the LEDs was working by connecting the yellow and black wire directly to each LEDs inputs. Then basically all I did was disconnect the non-working LEDs and connect the working LEDs to the yellow and black power inputs. This way I was able to get three LEDs powered and hopefully this is enough to get me past the annual state inspections. To me though the 3 LEDs now seems plenty bright even though it has only half of the LEDs working.