Prime Stall Shut Down

Car brake systems do have redundant systems. There is at least two separate hydraulic systems, and separate circuits for the electronic side is easy to do. Of course, like airplanes, having redundant systems doesn't mean they can't all fail because all the circuits happen to go through an area where mice can reach them all, or a single piece of debris can cut them all.

For those new to the Prius or hybrids in general, there is a pressure accumilator in the brake system. It is there for the same reason turbo charged engines have them, there isn't enough vacuum pressure to power boost the brakes as there is in a natural aspirated engine that is running all the time. The accumilator holds extra vacuum for the brakes for when the hybrid engine is off, and works in the event of unplanned engine power loss. So in a car with one, you have more use of the power brakes in the event of an emergency. The Prius also has a capacitor to power the brake electronics in such an event.

Toyota has had faults, and their design choices are fair reasons to not choose them, but rodents can wreck the wires of any car.

 

Yep, and just like with failed power steering - electric or hydraulic, doesn't matter - a driver can still brake and steer, because there's still mechanical linkage. Yes, it's heavy, and probably feels like brakes and/or steering is shot, but it's not. Scary, inconvenient, but not absent.

 

I've had a situation where the car still had power brakes, seemed to have most brake function, but went into (as the dealership service manager described it) a "default" or "fail-safe" mode. This was with our third gen. The brakes still "worked", but it seemed to take more effort, and they weren't as linear.

In our case they eventually pointed to the constant OBD connection I had for a ScanGauge, was causing temporary communication breaks. And having not seen more instances after disconnection, I'm inclined to agree.

 

The more of these threads I see with the car only being 1 or 2 years old, makes me wonder if the Toyota Care extended warranty is worth it. The ECU on this car seems more complicated than I was expecting. I still haven’t bought the warranty but I might be tempted now. Got quoted $1545 for 10yr/100k, any ecu problem at the dealer will cost that in one visit.

 

We actually had the expert that investigated the prius/camry sudden acceleration come in and give my department a talk on good reliability engineering practices. He came out and stated that the prius control software had something like 5K global variables. Almost all functions worked by modifying globals instead of the normal method of passing parameters and returning a result. As a result it was impossible to verify program correctness. Because every system was completely interrelated, and was missing a whole lot of needed mutex's there was no way for him to determine if the code was doing what it was supposed to do or if there was a chance that the unintended acceleration was due to a software bug.

 

Then why don’t we have anymore u/a?

 

Ecu issues are uncommon and very old cars typically.
What’s being discussed here wouldn’t be covered since there’s no fix.
If a fix does come, there will be a free recall

 

You are correct about how the pressure accumulator works, but there is some weirdness in this system, maybe related to the regenerative braking or the ability of the cruise control to apply the brakes. To demonstrate this, try sitting in the car with the door closed and the ignition off for a few minutes (5 minutes?). If it's like mine, when you try to press the brake to start the car it will be extremely firm, then it will suddenly release. There is still accumulator pressure stored since the pedal becomes normal before you can hear the brake booster pump start to run, so it hasn't all leaked out. There's a thread about this on here somewhere.

It's plausible that during an electrical malfunction the brakes could get stuck in this extremely firm mode that feels (and probably acts) like there is no power brake pressure. The brakes will probably still work, but you'll have to put a lot of weight into the pedal to stop, and you might not be able to stop as quickly as you need to.

Toyota has been doing electric assisted power brakes for a long time. For example the 4th gen 4runner which first came out in 2003 has an electric power brake system. But the system in the Prius seems to be a lot more sophisticated. The 4runner obviously can't do regenerative braking, and it has no way to gently apply the brakes like our cruise control does. It can only slam on the ABS if it needs to help you apply the brakes. For the 4runner there are just an handful of reports on the forums about brake pump failure, and only a couple that I can think of that are a catastrophic failure (loss of power brakes while driving). So it's generally pretty reliable, but really expensive to replace if it does fail.

Unfortunately with the Prius there is no real way to downshift, so we have one less failsafe way to slow down if there's a problem with the brakes. B mode is pretty weak compared to using a low gear, and it probably won't work if the hybrid system decides to turn off.[/QUOTE]

 

Why don't Toyota engines sludge up anymore? Toyota fixed the issue. No reason why they couldn't do the same with the brakes. Even if they didn't touch this control software, I'm pretty sure Toyota installed a brake interlock. Expirence uncontrolled acceleration, and hit the brakes, the engine throttle is killed. So even if the brakes aren't getting applied, the car is no longer accelerating.

[/QUOTE]I think the Prius is brake by wire, and that firmness is likely the system shutting down in order to not drain the battery while parked, or the capacitor has drained. A malfunction that causes a power loss could lead to that firm feeling during an emergency, except the capacitors are there for emergencies. Even if it only holds enough charge for a few minutes, that is more time than you need in such an emergency to get the car stopped.

 

f people were having u/a, and the brakes were killing the engine, i think we'd hear about it.

instead, we've heard a couple claims of u/a, but the car wouldn't stop.

 

what I said was that there was no way to prove the correctness of the software under all circumstances. The use of non mutex guarded global variables in a multithreaded system is poor beyond the pale. This goes against everything you're supposed to do in safety critical applications. These standards, admittedly, vary by application. However in almost every standard the use of globally visible variables is forbidden except in specific circumstances (for which these 5K plus variables were not).

now, the software *may* have been safe, it *may* have even been safe by deduction. However, because of the design there is no way to prove that it is safe and this is a major fault when you're dealing with safety critical software.

Besides the safety issue, it's actually hard to believe they got it working as well has they have. That's just piss-poor, un-maintainable code from any standpoint!

 

If there is a brake interlock, it was added after the unintended acceleration issue became a problem for Toyota. The brake interlock may have just been something getting discussed at the time.

In the most well known case of u/a, the accelerator got jammed down by the doubled up floor mats. The car was on the highway, so was already traveling at a high speed. Applying the brake, and reports make it sound like those were working, didn't work because they couldn't apply enough force to slow the car while the engine was applying power to accelerate the car.

Other cases of u/a that weren't user error, happened because the accelerator got stuck after being fully depressed. Toyota fixed those issues. So the chance of an u/a event happening when, of if, an interlock in place had dropped. Then the events could have stopped being news worthy. "The car sped up, but stopped as soon as I hit the brakes", isn't exactly eye catching.

The case in which this expert testified may not have been an u/a one. It happened at a ramp or intersection. The Camry ran off the road, possibly into a body of water, and the driver died. Details are murky to me at this time, but it was at speeds at which working brakes could have slowed or stopped the car if u/a was involved. Maybe the brakes were actually working, but the software was such a mess that there was no way to prove that it wasn't at fault.

Toyota's criminal fault arose because they were getting complaints about u/a and brake issues in other countries, but didn't report them to NHTSA as required.
2009–11 Toyota vehicle recalls - Wikipedia

 

Update: Toyota fixed the car ($100 my insurance deductible). Rodents can truly chew any car, but this barely 5 month old car shares the stable with 2 German and 1 Swedish SUV which remain untouched (touch wood) for last 5 years! Toyota fix included wrapping the “highly edible” wiring with grey “anti rodent) wiring.... I was advised to buy some at the local auto store and wrap other harnes....well for $34K you get what you pay for!!!
I now know why Stuttgart charges a premium for their products .. well worth the free cardiac stress test...shame on you Toyota!

 

As a long time German cars owner, I can give plenty of examples of what they should be ashamed of.

 

Hummm, another thing to watch out for my PRIME. I live in area with fairly high concentration of field mice, but never had problem on my previous cars. Have there been any suggestion on how to prevent this happening to PRIME? Are all Toyota cars prone to rodent chew?

 

Post #33 mentions an anti-rodent tape.

 

Lol I hope you are joking. The German car I owned is the biggest piece of junk I’ve ever seen. They use plastic gaskets and components that degrade very fast and cause oil leaks, the electronic modules are prone to failure. I’ve had an abs pump fail on a German car that was 6 years old. Google BMW HPFP recall to see the disaster the 335i high pressure fuel pumps are. The issues are too many to count.

I paid 24k for a Honda and parked it outside for 10 years and never had any rodent damage. The car’s price has little to do with the quality, you just have a rat problem in your garage. Might want to get an exterminator before it happens again.

 

I really have to wonder what it is made of? Is it toxic enough that would deter rodent to avoid it??? Hummm, if I am to do preventative measure, I have to first identify which wires are “highly edible”. Or, all of them are tasty?

 

I believe it would be easier to hinder access points than try and cover all the wiring harnesses. There are lots of threads about doing this on all Prius models and they would be applicable to the Prime. The biggest is the fresh air intake which is pretty wide open. Pay particular attention to the PiP threads as they have additional fresh air access for the battery.


iPhone ?

 

We've had issues with chipmunks and mice scampering about the tractor (stored in a shed) and seem to be keeping them at bay with moth balls (in nylon sacks) placed under the cowling. We use poison bait traps inside the shed as well. If that doesn't work, you can always get an outdoor cat!

We're less concerned with rodent damage since this guy paid us a visit!