Hazard Lights blinking continuously

have you find out why it was flashing? i have same issue on 2010.

 

Visual version of Prius "sound generator"?

 

Shorted ABS module. Replaced with one from salvage yard.

 

well done!

 

too bad o/p didn't hang around to learn the fix

 

My 2012 Gen 3 (140k miles) had continuously blinking hazard lights that would not turn off. Blink rate constant regardless of road speed. Based on suggestions from this forum, I bought a used brake master cylinder assy which includes the ABS module from Benzeen Auto in CA (~$150). Long story short, this fixed the issue.
However, it's not an easy install. As a weekend warrior, it took me a good 10 hours. Now that I know how to do it, it would take me about 5 hours including bleeding the brakes.
The 4 nuts securing the master cylinder in the footwell were especially frustrating. 3 of 4 were easy but the fourth is right behind the steering column. I finally got it with a deep socket and a swivel adapter on my ratchet wrench. Also, to free the clevis pin, I destroyed the fancy clip holding the clevis pin. I replaced it with a good size cotter pin.
One good thing about doing this on a Gen 3 is that you don't need to do anything to the inverter.
I bled the brakes without Techstream and without putting the car into "invalid mode". After filling the brake fluid reservoir, I pumped the pedal about 30 times, then did the rears first. Hold steady pressure on the pedal so that the pump runs. Bleed both rears until no more air bubbles emerge. For the fronts, have someone slowly pump the pedal while bleeding both sides. Make sure there's adequate fluid in the reservoir while bleeding the brakes. That's it. Brakes are nice and stiff. I used a full 32 ozs of Dot 3 fluid.
Finally, if your brakes lights stay on with the replacement master cylinder, the switch at the upper end of the brake pedal needs to be adjusted.

 

The steady four-way flasher blink could also be the onboard alarm, although normally accompanied by the horn.

 

Weirdly, there have been multiple threads here on PriusChat about this exact failure. The lights seem to be controlled by the skid ECU, and it also has another responsibility: because it has the wheel speed sensors, it has the job of generating the 'vehicle speed pulse' signal, a train of pulses at a rate proportional to road speed. The speedometer and nav (if present) are users of that pulse signal.

So it seems that something kind of regularly fails inside the brake/skid ECU so that the speed pulse signal gets crossed with the hazard lights. A pretty comical failure mode ... at least, it would be really funny, if it weren't such an expensive part and repair job.

 

2012 Plug-In here. This just started happening soon after the last recall they did. Of course that was months ago and I've been dragging my feet to get it fixed. Plus it went away for a while. Given the numerous cases do you think this is something we could go to corporate about for a safety recall?

 

My Prius V 2013 just started to do the hazard flashing but I also have a lots of lights on in the dashboard : Handbrake light (red exclamation point), anti-skid light, abs light and the yellow exclamation point. I will have a look at the abs module, thanks to this forum. Has anyone had the same lights in the dash issue?

 

My 2012 Prius (not sure the sub-model) started doing this the other day. All the dash lights came on as well. I found a youtube video of the diagnosis, it was the anti-skid eco. Unfortunately, I can't find mine in the same place as the video...

Not sure if we're allowed to post links here, but if you google '2012 prius hazard lights blinking constantly' it will be the first result in the list

Does anyone know how to get to the anti-skid ECU?

 

It's this gizmo, mounted on the firewall in the engine compartment, right where the brake pedal is (the pushrod you see attaches to the pedal).

It's one unit that's the ECU (inside the flat ribbed side you're looking at here), plus the master cylinder, booster, stroke simulator, and actuator. The ECU doesn't come separately.



The goofy-hazards business is common enough to be known around here. Here is the thread you'll want.