Catastrophic brake failure Gen3 Prius

this is very common with the prius. when you feel the brakes 'slip', press harder. it usually happens at low speeds when transitioning from regen braking to friction, in combination with traction control.

besides the recall, there may be a software update available to you. plug your vin into the toyota owners website if that is offered in the u/k.

 

You're not describing catastrophic brake failure, you're describing what every Prius does if it gets triggered to switch from regen to antilock braking in the middle of a moderate use of the brakes.

Not really; it drops the regen immediately to make sure it can't lose steering traction, and brings in the four-wheel ABS within a split second. Because any urgent braking (detected by the pedal angle sensor rate of change) goes straight to ABS from the start, this is a behavior you can only experience in moderate braking situations, and I've never had the split-second that it takes ever bring me anywhere near hitting anything.

When I first bought my Gen 1 ten years ago, posters right here on PriusChat advised me to just go out on some gritty, potholey road and do moderate braking until I was used to how it felt. That's still the best advice going.

Now, if you've got a 2010, it would not hurt to just check that the A0B recall was done on it. That was a software update. It didn't eliminate the regen-to-ABS transition (something every Prius model has always had), but there was apparently something about the early 2010 software that made it feel scarier to more people, and the A0B update toned that down somehow. (Maybe it changed more than that; we the unwashed don't get to read the source code.)

You can either look up your VIN on the Toyota Owners site and see that the recall was performed, or look for a sticker about it, or use Techstream and get the software version from the brake computer. If it is F152647106 or later (if you have 15 inch wheels) or F152647126 or later (17 inch wheels), the recall was done (or the car was built late enough not to need it).

Edit: I just noticed your location ... I do not know whether the USA recall identifier, or the USA left-hand-drive software version numbers will be right for you, but the general information holds.

-Chap

 

After reading, this is not a catastrophic failure. It’s normal for Prius brakes to slip on potholes, bumps etc.

The fix is to buy another non Prius vehicle, like Honda Civic hybrid.

 

Jerry Harris - think you will find this interesting

Are the Brakes Defective in Gen III and Gen II Prius Vehicles? - ToyotaTalk

 

@Jerry Harris how many miles on it? And how was it initially deemed that there was a misfire in cylinder #1?

FYI, getting to the spark plugs is a royal pain: the wipers, their motor and linkage, bottom of windshield trim and a large metal cowl, all have to be removed. Lots of cables need disconnection, and there's maybe 30 bolts to remove. Just to get to the spark plugs, lol.

 

Glad others have clarified this issue. We all get it, that split second of "!!!" when, under just the right conditions, you feel that swap from regen to friction brakes. This only happens on a slick surface to me, so I assume TC is involved somehow in exaggerating this transition, which you otherwise don't feel much.

I have a regular turn I take in my town that triggers this frequently, there's a manhole cover right in the braking zone and if it's wet and I hit it just right, I cna "make" that "!!!" feeling happen.

I agree, it's disconcerting when you don't expect it, or know what it is.

 

IT'S NOT DISCONCERTING, IT'S CATASTOPHIC!

 

this is in no way related to what the o/p is describing

 

He needs another story.

 

It's not just slick surfaces ... there's a pothole on the way out of my neighborhood that'll do it every day without fail, wet or dry. It isn't traction control, it's just the brake ECU switching from regen braking (all done with the two front wheels) to ABS (done with all four) for better control. It is triggered by the ECU thinking you might be losing traction, but you don't have to be really losing traction. Taking one wheel over a bump or pothole momentarily gives the ECU different speed signals from the wheels, just because one wheel is legit rolling a different distance than the other. But the ECU doesn't know that, so it makes the conservative choice. Has to get explained on PriusChat over and over because people don't search.

Interesting web site, that. The article has a lot of pieces of individually-true information, and useful links to a lot of the different brake-related fault analysis reports, recalls, and service campaigns. But at the same time it seems to go to great deliberate lengths to blur issues together to seem as if they are related.

Of the NHTSA reports it quotes, the fourth one is clearly about this regen-to-ABS transition:

This is the familiar every-Prius-ever-made oddity. It surprises people who somehow haven't been told about it, but these cars have been around 21 years now and there are plenty of people around to pass the information along. Here's my own thread asking about it 10½ years ago in the first month of owning my first Gen 1 (because it hadn't happened to me yet and I had read about it here) and having it explained to me. There are always some questionable explanations in circulation too, but I was lucky and got Tom's reply first.

But back to this ToyotaTalk piece. The first three NHTSA reports it quotes are not about this issue at all, but about some very different reports where drivers say they pushed the pedal to the floor and the car kept right on going. One of them says nothing about warning lights, one says explicitly there were none, the third says there were a bunch of them.

Those would be the kinds of "catastrophic brake failure" I'd be most interested to know more about, because (a) they don't match any of the known brake issues we usually discuss here on PriusChat and (b) they really do sound "catastrophic". I wish I knew more about them, but they seem to be rare enough we don't have much to go on here. But meanwhile this article keeps on mixing up all sorts of issues together.

It provides a link to the "defect information report" for the A0B recall, which is the one about the regen-to-ABS transition, which apparently was more noticeable in early 2010s than in the previous generations. It says they made a "running production change in January 2010" to the ABS software to improve the response time. In February 2010 they decided to make it a recall and reflash existing cars' ABS ECUs also. My 2010 already had the newer firmware when I bought it, so I have never felt what the transition was like earlier. With the new firmware, I can vouch it feels pretty much like my Gen 1 did.

But then the article goes on to sow confusion between this issue and the one for recall D0H. D0H was the physical recall of the pressure accumulators that could form internal hairline cracks and leak nitrogen into the system, a distinct issue from the regen-to-ABS switch. Usefully, the article links to the defect information report for D0H. I had read the TIS literature about D0H before, but never this particular report until now. It's nice to read what the underlying issue was. The accumulator in Gen 3 lies horizontally, a cylindrical can with the Slinky-like pleated metal bellows inside. Here's a metal bellows accumulator from a hydraulic equipment site (not exactly the Prius part) to show the kind of animal:



It seems that in some of the accumulators used before September 2009 (these are the ones with the label horizontal on the can), the bellows inside was a bit smaller than the design diameter, leaving more clearance for it to be shaken up and down inside the can on bumpy roads. When shaking up and down, it hits the lower inside surface of the can hard, and that's where it forms the hairline cracks. When the bellows is closer to the design diameter, it doesn't have as much clearance to shake, and doesn't get banged as hard on the bottom of the can.

The D0H recall was about bringing in cars with the too-shakable accumulators and replacing the accumulators with the ones with the proper internal clearance.

... and then the article brings in T-SB-0363-10, which was about an improvement to the ABS ECU firmware to reduce a quacking sound made by the actuator:

Well, or you could just say they released an -06/-26 firmware version with the A0B recall to speed up the regen to ABS transition, and they later released an -08/-28 version to quiet a quacking noise? It's not like the later change for another purpose "superseded" the first one. Does the article's author somehow think the skid ECU firmware has exactly one line of code?

The article brings in another NHTSA complaint:

Notice what this driver is experiencing is the opposite of the first three reports (low, soft pedal with no brake response). This driver is talking about a high, hard pedal that has to be stood on to stop the car—in other words, not a loss of braking but a loss of power assist. C1391 is a code that reports either the pressure in the accumulator doesn't rise fast enough when the pump runs, or it drops too fast when the pump is stopped and the brakes aren't being used. That tends to mean something is allowing the pressurized fluid to escape back to the reservoir, maybe a release valve in the actuator that isn't fully seating. If you run out of assist pressure, the pedal is very hard; you have to make the pressure yourself. You can feel what it's like if you do the non-Techstream zero-down procedure in a Gen 1 or Gen 3. (Doesn't work in a Gen 2 because the system is different.) You know you've used all the pressure when the pedal stroke suddenly feels like you stomped on a rock.

Next, the article wanders around to question how the D0H recall instructions could possibly have used the accumulator label orientation to tell the good ones from the shakable ones:

... well, um, not so far inside ... the accumulator is the black can there, the one with the label on it.

This is funny, considering the article links right to the defect information report, where Toyota said they switched in September 2009 to an updated accumulator. And then it goes on:

Riight, because, remember, the A0B recall was the software change to speed up the regen to ABS transition ... not anything to do with the accumulator?

It goes on to mix up several more things, but I'm ready to call it a night. Not only is the article's author anonymous (it's written by "ToyotaTalk"), the whole web site is anonymous. It has no "about" saying here's who we are, it has a "contact" page that gives you no contacts there, only a message form you can fill in or an anonymous address to mail to. Even the domain itself, toyotatalk.com, is registered with GoDaddy under DomainsByProxy so you don't see any info of who's behind it.

I am not a reflexive defender of Toyota in everything. The "Task X" design that came to light in the unintended-acceleration trial was legitimate facepalm material. But this article was an obvious hit piece from anonymous sources, providing links to a lot of genuine, interesting information, but mixing it up in irresponsible and tendentious ways. Yuck....

-Chap