Brake, ABS, VSC warning lights all on

gromittoo · Jul 5, 2021

I am just impressed that he found a Toyota Dealership service department open on July 4th Observed.

Merkey · Jul 5, 2021

ChapmanF said: ↑

As Air_Boss points out, Merkey's situation doesn't have to be the same situation, just because the dash lights are on. As always, it could be any of a great many things, and the best way to proceed is just to retrieve the trouble codes and then troubleshoot whatever they are reporting.

The trouble with trying to learn anything useful about technical matters with the brakes from reading a class-action complaint, at least one like this, is that the reality of any technical matter is of no interest to the lawyers, as long as they can talk a (usually tech-naïve) judge and jury into a money award.

The biggest tell in this complaint is the way it refers (over and over and over again) to "the Toyota Brake Defect" (singular 'the') and never in 165 pages gives any hint what they think this overarching "Defect" might be, while the complaint is stitched together by taking reports of different issues that have known different causes and effects, and indiscriminately glomming them all together under this invented notion of "the Toyota Brake Defect".

Paragraphs 92–93 are about the accumulators that developed early leaks of nitrogen gas into the brake fluid, because a certain run of them were manufactured with the bellows out of size tolerance. (Those were replaced under a true recall, available to everyone who had them; you have to be careful when shopping for used ones to avoid resold ones from that run.) It's possible that even units outside of that run can still eventually leak some gas after a long enough time in service; I'm not sure what a reasonable service life for such a part ought to be. It can currently be replaced for free if it wears out within ten years or 150,000 miles.

Paragraph 94 is about internal hydraulic fluid (not nitrogen gas) leaks developing in the booster-with-master-cylinder assembly (a whole other part from the accumulator assembly discussed in 92–93). There are fewer details published about why these leaks develop: there are numerous small valves in the actuator, and I haven't seen any defect information report that pins down whether it's one valve in particular that usually goes, or could be any of them, whether the valve gets stuck, or its seat erodes, or grit gets stuck in the seat, etc. The warranty extension will also cover this issue out to ten years or 150,000 miles (or through the rest of this year regardless of mileage.)

Paragraph 95 is about the electric pump in the system ceasing to pump because of its electrical brushes getting stuck in a misshapen brush holder. They figured out which plant made those brush holders, and which shift installed the bad molds in the machine, and which units those brush holders got installed in, and those were replaced in a recall.

So it turns out the brake system is a piece of electrical/mechanical/hydraulic reality where specific things happen for specific reasons; you just won't learn about that from a lawyer yammering for page after page about "the Toyota Brake Defect" with no one venturing even a guess what this alleged overarching "defect" might be.

Maybe they're mostly thinking it's that middle issue, the one about the hydraulic internal leaks developing in the actuator. That seems to be the one we know the fewest details about; I'd like to know more. I'm sure eventually more will be learned about what's going on there; that will have to be figured out by people able to tune out 165 page lawyer screeds and manage to focus on what is and isn't technically happening.

Besides being a hodge-podge of known different causes, the complaint is also not bothering to distinguish between very different effects:

Effects of accumulator nitrogen gas leakage

Reduced volume of gas in the accumulator where it belongs

When the gas volume in the accumulator is reduced, it takes a smaller change in brake-fluid volume to make the same change in system pressure, so the pump has to run more often. This is just like a home well-water system when the air charge in the pressure tank is too small.

Gas leaked into the circulating brake fluid where it doesn't belong

Nitrogen in the wrong place will be bubbles that have to be compressed when the brakes are applied, just like in any brake system that needs to be bled. In an old-fashioned system, you would immediately notice the pedal being spongy. In this system, you don't immediately notice, because the brake ECU is in charge of the valves and will send as much fluid as needed to reach the target pressure, so the brakes continue to feel about the same (though you may hear an extra whoosh-like noise). However, this means more fluid from the accumulator is moved with each use of the brakes; on release, the bubbles expand again and drive the additional fluid back to the reservoir. This effect also means the pump has to run more often.

So both effects of nitrogen leakage tend to make the pump run more often. The effects of gas getting into the circulating fluid can be corrected by doing a brake bleed and letting the gas out (even if you would normally only do that after opening the system and letting air in). Of course nothing you do puts nitrogen back into the accumulator, so that part of the effect will simply progress over time, and the pump may eventually be running so often that accumulator replacement is needed.

Effects of actuator internal leaks of hydraulic fluid

If some return valve(s) in the actuator assembly don't seal perfectly when shut, there can be a constant slow loss of accumulator pressure when the brakes aren't being used, making the pump have to run more often to keep the pressure up.

So "pump runs more often" is a common result from this cause or from nitrogen gas leakage out of the accumulator, but the two causes are different. If the pump isn't running repeatedly while the brakes aren't in use, but only runs more often when they're used, nitrogen leakage may be involved. If the pump has to cycle repeatedly while no one is doing anything with the brakes, this hydraulic leakage is probably involved.

Effects of the pump not running

If the pump doesn't run (whether because of a jammed brush holder or for any other electrical reason, or the pump is just worn out), the effect is, well, the pump doesn't run. The brake fluid pressure in the accumulator gets used up a little with each use of the brakes. After normally twenty or thirty uses of the brake, there won't be enough pressure to provide braking assist, and the brake pedal gets hard and needs a lot of extra leg pressure to stop the car. That's what "loss of braking assist" means.

Stuff happens before the braking assist is lost. The ECU has codes to set (lighting dash warnings) as soon as it detects the pump isn't pumping, while you still have stored pressure in the accumulator. Additional codes will be set as you use the brakes and begin using up the stored pressure. When the pressure gets down below a low-alarm limit, a high-pitched beep alarm will join in with the dash lights. After some more uses of the brake from that point, eventually, the pressure is all used up and you lose assist, and have to step really hard on the pedal to make the car stop.

So how did the lawyers turn that into "and if that happened, Toyota explained, the result could be a 'sudden and complete loss of braking assist'" as they did in paragraph 95?

Easy: they just took what Toyota actually wrote

and just lifted out the colored part. (Even though that sentence starts with "A sudden ...", you can see how they started their quote at "sudden", to get around the legal quoting rules for showing changes, as "[a] sudden" would have given away that they were lifting this bit from a whole new sentence.)

They also play fast and loose mixing up very different symptoms:

Loss of braking assist

This is where the pedal feels high and hard, and you have to apply really firm foot pressure to make it slow or stop the car.

Loss of braking

This is where the pedal is low and soft, or goes clear to the floor and doesn't stop the car, no matter how hard you push.

None of the above

The lawyers also threw in a bunch of complaints from drivers who apparently just never had anybody explain to them how the regen-to-hydraulic mode switch during gentle braking on a weird surface always feels, and reacted with panic.

(While that really doesn't belong in this complaint, it's clearly something here on PriusChat we used to be better about explaining to new owners. We can still see it flustering new drivers if they haven't gone and found a bumpy road and tried it a few times to learn how it works. TL;DR, just keep your foot on the pedal, and press a little bit harder to make your original stopping target if you're set on it.)

For all the different technical issues being mixed together here, the usual effect is always a progression of warning lights, lights and buzzer, then eventual loss of braking assist (so you have to push firmly on the hard pedal to stop the car.)

There have been some reports of loss of braking (thankfully, those reports are much rarer). There hasn't really been a clear explanation of those; I have a speculative one involving a very late stage of nitrogen leakage.

It's helpful to learn more about all these things, but a big document written by lawyers inventing some singular "Toyota Brake Defect" just isn't much of a source to learn from.
Click to expand...

Great summary. Thanks.

Merkey · Jul 5, 2021

harold said: ↑

Just heard the good news. It is the ABS - Brake booster issue and covered by Toyota. Car should be ready Thursday or Friday.
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My Scan Gauge says no codes found. Does it have to be an official Toyota scanner to show codes?

rjparker · Jul 5, 2021

harold said: ↑

Just heard the good news. It is the ABS - Brake booster issue and covered by Toyota. Car should be ready Thursday or Friday.
Click to expand...

Good news indeed but, frankly, expected. Not quite hitting the lottery when thousands of others have received the same consideration (including me years ago). I think the 800 lb gorilla is the head gasket issue, also experienced by many for years but now approaching critical mass. Excuses abound but its clearly a design flaw that manifests in a slow, intermittent fashion. I hear the Iranians are developing a secret egr stockpile based on Mendel's recommendations. Hopefully Microsoft has hidden code in the valve.

ChapmanF · Jul 5, 2021

Merkey said: ↑

My Scan Gauge says no codes found. Does it have to be an official Toyota scanner to show codes?
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It might be possible to program a ScanGauge to retrieve brake system codes.

Conveniently, the brake system in Gen 3 still has the ability to blink out two-digit codes on the dash lights. Getting the codes that way eliminates any dependency on a scan tool, and eliminates all those "are these really the codes, or is it my scan tool?" questions.

harold · Jul 8, 2021

Just picked up the car. Asked what cost would have been. $3,239.16 which would include 3 days rental car loaner. I’m happy!

Air_Boss · Jul 8, 2021

Big win, even if not MegaMillions level.

harold · Jul 8, 2021

Air_Boss said: ↑

Big win, even if not MegaMillions level.
Click to expand...

I’m happy!

harold · Jul 10, 2021

Are there any other consumer support programs for our Prius V’s like the one for the break booster/abs?

Tim Jones · Jul 12, 2021

harold said: ↑

Just picked up the car. Asked what cost would have been. $3,239.16 which would include 3 days rental car loaner. I’m happy!
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Toyota told me $2100 when they fixed mine...............

harold · Jul 14, 2021

Here’s another customer support repair program Toyota covers

https://static.nhtsa.gov/odi/tsbs/2018/MC-10149999-9999.pdf

Tim Jones · Jul 14, 2021

harold said: ↑

Just heard the good news. It is the ABS - Brake booster issue and covered by Toyota. Car should be ready Thursday or Friday.
Click to expand...

Make sure you have the firmware update for the inverter and that will be done with the new brakes..... because the Power module inside it will blow next.....and leave you stranded....

harold · Jul 14, 2021

Are you referring to the firmware update that was done under the recall?

Tim Jones · Jul 14, 2021

When ever u go to toyota they are supposed to make sure your up to date.....

harold · Jul 16, 2021

Heard the booster pump come on a couple of times while stopped,not like before where it was always constant but I’m now keenly aware when I near it. how often is it supposed to come on?

have a great weekend

Air_Boss · Jul 16, 2021

I only hear ours on pre-startup.

Tim Jones · Jul 16, 2021

another toyota blunder..... yes they fix it.....but really bad if your on a trip. Very inconvenient.
I know firsthand.....inverter, brake system and head gasket......did put a new traction battery in but was expecting that. And of course the entire EGR System was Plugged.

Kind of a screwy car but they do get good mpg.

Brake, ABS, VSC warning lights all on

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