Hazard lights gone crazy

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I have the same problem and would also like to know exactly which part was replaced. The dealer said they have never heard of this problem. Thank for your help!

 

Hey guys, I had this problem too and I sort of fixed it a different way. It was a little bit different in my case because when I pulled the ABS fuse, the problem would NOT go away. I took it to a local mechanic, but he couldn't figure out what was wrong and referred me to the dealership, where I did not want to go.

My solution to this was to pull the pin from the L55 hazard pin and then jump a wire to the hazard button manually via soldering. I suspect a short developed on the harness to something that I don't know about and my solution was to basically disconnect that connection. By doing this, the skid control ECU and main computer no longer drive the hazards, so when you press the unlock on the key fob, the lights no longer flash. But everything else works normally. I have a post with a detailed analysis of what I did if you want to click on my profile.

 

Hi @xywang84, I have the exact same problem. 2011 Prius hazard lights blink faster when driving and slow down to a normal blinking when stopped. I have to pull the haz/turn fuse under the hood to stop them but I have no turn signals now. Please tell more about how you jumped your wire to make it work normally and did your turn signals work?

 

I no longer have the car. But basically you can buy the relay for 15 bucks online. I bought an extra relay just in case that was the problem but the relay ended up being good. The relays have male pins inside them and the hazard pin is the I believe the 8th one (do double check). I pulled out the pin with a pair of pliers which causes there to be a stump where you can solder a wire on. I went in from the side, burned a hole in the relay casing with a soldering iron and then soldered some 30awg wire onto it. I then inserted the relay back into place and ran the wire over under the dash to the hazard button (which requires removing the dash). For the hazard button I snipped off the existing wiring and then jumped the other end of the wire to the stump.

 

Thanks Xywang85, I didn’t have a lot of time today but I did pull the flasher relay out. I pulled it from underneath the left side dash. It’s way up in there and I had trouble seeing it. So I removed the plastic cover from under the steering column. This way I could watch while I reached my arm underneath to pull it. It was hard to pull out! Had to wiggle it all around and then it popped. I’m going to try soldering a wire as you said next.

Hi xywang84, I opened the flasher relay and used my soldering iron and removed pin 8 from board of the relay at L55. Then I soldered a small wire about 3 feet long to it where the pin was and made a hole with the soldering iron for the wire to come out. I found the yellow wire at the hazard button only had ground when button was depressed. I cut the yellow wire and soldered the wire on from the relay “pin 8” to it and taped it. Signals and hazard flashers now work normally. Only the key fob no longer blinks the lights. A fine trade off. Now we can safely drive! $0 spent to fix this! Thank you so much!

 

Ok, this is apparently not a problem that is unique in all the annals of PriusChat. It's been reported multiple times on this thread and this other thread.

More than one person has "solved" it by disconnecting the wire that is supposed to trigger the hazard relay, under control of an ECU, and instead just running a wire straight from the hazard switch on the dash to the disconnected relay pin.

I get that it's a solution that kinda gets the job done, but I'm still itching to see somebody complete the diagnosis of what's really going on. The "blinks faster with road speed" is such a monumental hint: one job of the skid ECU is to generate a faster-with-road-speed pulse signal for the combo meter and nav to read, and I see almost no other way to complete this story than with that signal somehow being crossed onto the hazard relay trigger signal ... either in damaged wiring, or somehow in circuit-board damage or semiconductor damage in the ECU somewhere.

PriusChatters have found board-level solutions to other Prius electronics problems before, so maybe one can be found for this too. It might not even be that much harder than the "just cut and splice the wire" solution ... it would be one thing if the just-cut-and-splice were a five-minute job, but if one is taking the dash off anyway....

 

It sure would be great if someone could actually fix the short! Unfortunately I could not figure it out! Im so happy to have found here a way to jump a wire and now be able to use the car again safely. It may be harder to find in the parking lot now since the lights no longer flash with the key fob! This job took me about an hour and cost $0! If someone ever finds a way to fix the short properly I sure would like to do that!

Leslie

 

@ChapmanF I did think about debugging this further. But after the wire splice "solution" worked enough for me to get by I got lazy about additional debugging. Also the wire splice only involves removing the radio dash parts which were fairly easy. Getting all the way to the junction block 3A and 3B required what I recalled to be a much more extensive dash removing process which I wasn't super motivated to do. You're absolutely right that it would be awesome to find a comprehensive solution, and I too suspect a short somewhere on the harness as the main culprit.

The additional piece of info that was kind of scary was that before I did the fix, the entire brake system light came on one time during driving. It eventually went away, but it basically eliminated the regen braking temporarily and it was probably another symptom of the short. I drove the car for maybe another half year after the fix, and no issues ever popped up, but this was sufficient for me to end up selling the car to a dealer on a trade-in for a new Ioniq PHEV.

 

So this just started happening on my 2010 prius as well, except it's opposite of what others have described. When driving at a slow speed it flashes light crazy but when driving at higher speeds it disappears or very rarely flashes.

I've noticed that it flashes more often when decelerating and accelerating then driving at constant speeds. Manual driving or cruise control has the same effect on it.

I've tried to get my VCI running but having issues getting it to work with Windows 10, will have to try tomorrow to see if I can further information.

Any suggestions on other things I can look at? Can't see anything noticeable in terms of vermin damage but will have to look further in the daylight.

Thanks in advance

 

Could be a different type of short going into the hazard light harness. Does it keep flashing while the car is turned off as well?

If it is a short on the harness, the fix that @Leslie Howard described should be good for that too, as it literally disconnects the hazards from everything that could possibly drive it, and replaces the connection to the physical hazard button.

 

Hey Leslie do not know if you'll see this, but any recommendations for route to thread the wire? I'm going to figure it out now but thought I'd ask before I start removing pieces of the dash. Thanks for your helpful photos.