Intermittent tail light outage

Well, the problem is either the bulb, the socket, or the wiring harness. A common TAIL fuse provides power back to that area including the license plate bulbs, so if those bulbs light at all times then you know the fuse is OK.

Maybe you could focus on one side, and find the wiring harness and wiggle that to see if the light flickers. If not, then wiggle the socket while it is installed in the rear light assembly to see if you can get the light to flicker.

Once you've identified the part that is bad then maybe you'll be able to figure out what is wrong. Good luck.

 

Another good idea would be to order some high-quality LEDs to replace the bulbs. Lately I've seen an awful lot of low-quality bulbs coming out of China that fail often. A good LED unit should last the life of the car.

FYI: You need side-emitting LEDs for these.

I have replaced *all* of the incandescent bulbs on my car except for the reverse bulbs. I have had no troubles with any of them.

 

I think the bulb type (168) with small wire contacts along with the wire contacts in the socket create a problem. I think the current causes a flash over when you add some water. This creates a small amount of crud that insulates the two wires.

I have changed the 168 running lights to red 9 LED bulbs. I hope the smaller current draw will avoid the flash over.

I note that the 2010 Prius does not have these cheap sockets and lights.

 

I'm having the same problem with my '07. It started with the Left tail light going out. I replaced it with a bulb from O'Reilly's. This bulb went out 3 weeks later. So, I replaced it with the other bulb in the package. Now, 5 weeks later and many intermittent outages where tightening the socket back into the housing resulted in the bulb coming back on, the bulb is blown again. It is also now happening on the R side, but no bad bulbs yet. If I tighten the connector in the housing, it lights right up. I've jiggled wires, no change. Jiggled the bulb in the housing, no change. Very strange...

 

Remove the bulb holder from the wiring loom. Remove the bulb from the holder. When you look down into the holder you can see the 4 contacts.These contacts spread apart slightly and cause intermittent contact with the bulb. You can very gently push these contacts closer together. Spray with a good electrical contact cleaner and refit to your car.

 

I am dealing with a similar problem on my 06 that the OP describes, though mine only started after about 5 or 6 years of age.

For about a year now, I have a bad connection with both of my license plate bulbs, which I have both replaced. Sometimes just giving the area a pound brings it back on - though this seems to only work with one or the other.

Not sure if it is a wiring issue or a socket issue, but I am guessing it is probably the latter. I am going to give shaneb's suggestion a shot (thanks!), having a closer look at the sockets and attempting to clean them. Is there any particular electrical contact cleaner I should use?

It's just such a pain taking that panel off...

 

I'm having the same problem. This appears to be a common problem, particularly with '07s as I see a lot of posts on Prius Chat about it. This thread (use contact cleaner) seems to make the most sense to me as a first step. Personally, I use DeoxIT, it's given me the best results on other issues like this. I'll give it a try and post the results in here.

FYI, got pulled over a couple days ago for it. Not sure how to deal with it if I get pulled over again. I don't want to go to a dealer, get charged $300+ and still not have it fixed... only advantage I can see to that is if I did that, I'd have a receipt to show the cop and say "hey, I TRIED to get it fixed".

 

I had the same problem. I assume you are talking about the red running lights in back that are on all the time you have your headlights on. Well I replaced one and about a month later it was out again. After checking it I noticed that when the bulb is pushed in tight, there is a little play, so when the car hits rough roads the bulb moves and loses contact so it goes out.....I just pulled the bulb out just a bit until I felt the bulb become tighter. So far so good.....

 

This was the subject of a recall from Saturn on a vehicle we owned by them....almost the same exact symptoms. I think everybody with this issue should immediately file a complaint with the NHTSA before somebody gets hurt/killed from intermittent brake/tail lights!

 

We've had this issue ever since we got our car used in 2012. The lights would randomly be on and off. I always suspected it was a wiring issue. We had a mechanic look at it in July and they said the bulbs were out so they replaced them. Then a couple of months later the left light went out. And then it came back on a few weeks later!
Having seen some of the earlier posts here I decided to tinker with the bulb a bit. It is very tiny and flimsy! When I took it out, one of the wire leads was bent and I could see how that would lead to a poor contact, so I put I bent it straight. Voila! it worked.
However, being overzealous, I read the other guys post about the four contacts and pushing the contacts together so I did that. Bah! Somehow that blew the bulb out. do not know.
So I went to OReilly's to get a new bulb. When I was checking out the guy offered me to buy bulb connector grease. I thought why not. So I slathered some on the bulb, probably should not have put it on the leads! And went ahead and replaced the right one, too, since it seems like these bulbs were longer lasting.
Anyways, my conclusion remains the same, a wiring issue. Best solution seems to be to make sure the leads aren't bent and that they are making a good connection. do not know why it blew after I messed with the contacts.

 

"do not know why it blew after I messed with the contacts." My 09 tail bulb was intermittent, I tweaked the contacts and now the build is bad = broken filament!

 

I have a 230,000 mile '05 that I've had to replace several bulbs (every running light, 2 turn signals, and both license plate lights) on. After watching it eat regular (168) bulbs like candy (most lasted less than a month), I decided to try some LL's (Long Life) that, after more than a year, I've only replaced one (left front, running) of.
BTW, I also successfully did the fist bump on every one - for a while, then it didn't work - except the plate lights (they just straight up burned out). My only guess is that the contact wires are ever so slightly thicker on the LL's.
Now on to that pesky intermittent right brake light....