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Toyota Prius Software Problems
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Comments
"Also, if the engine's throttle-position sensor determines the driver has abruptly released the accelerator pedal, the braking system is programmed to provide just enough hydraulic pressure to move the brake pads up against the rotors, providing faster response in the panic stop."
"When you step on your brake pedal in a conventional system, you're pushing a piston that is pushing fluid out of a cylinder (think bicycle pump), through brake lines, to a hydraulic caliper that squeezes stationary brake pads against a rotor that spins along with the wheel. When you step on the brake in a Prius, your still pushing fluid with a piston, but instead of going to the calipers, the fluid goes to a "dead end" chamber with a piston that pushes on one or two springs. The only purpose of the chamber is to provide a pedal feel for the driver. When the brake is pressed with moderate pressure, the piston is only touches the softer of the 2 springs, providing a little give in the brake pedal. This simulates line and caliper flex normally felt on a conventional system. When brake pedal is pressed harder, the piston comes in contact with the second, stiffer, spring, providing a harder brake pedal, simulating the feel of a conventional brake system once the "slack" has been removed. The real braking work is controlled by a brake control computer, which monitors the brake pedal position with two redundant sensors. The brake computer then uses the electric motor / generator MG2 to slow the car and charge the battery or applies pressure to the calipers using pressure stored in the ABS accumulator. If there were a serious brake control problem, two solenoids open, by-passing the dead end chamber and computer control, allowing the brake system to function just like a conventional system."
I think that settles it. If there is a brake control problem, the computer control is bypassed and the brakes will work.
From this page:
http://www.artsautomotive.com/Hybrid.htm
Why would several people claim their brake pedal went all the way down without stopping them? I realize the person that hit someone from behind is wanting to place blame. The others did not have accidents. What reason do they have to lie about the brakes. You have no problem pointing at other cars that have had brakes fail. Why are you not able to accept that the Prius brakes just may have a problem? If I remember correctly you were a non believer about the stalling problem that Toyota accepted after the NHTSA started investigating.
From your last post on the Prius "Fake Brakes" it would indicate to me that the brakes are under the control of software, until the processor activates the two emergency solenoids.
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THAT is the thing that bothered me - people say "OH, THE PRIUS HAS A SOFTWARE PROBLEM" so that means EVERY PRIUS PROBLEM to come along gets blamed on the same software problem. That's just idiotic to think that is true.
Despite it's technological advancements in the way of computerized hybridization for the goal of achieving high mileage, the Prius is in many ways JUST LIKE ANY OTHER CAR including the redundant mechanical brake system.
Now, with all that said, there very well may be a SEPARATE brake problem on certain Priuses, but it's darn sure NOT because of the HSD computer.
There may be a part of the software problem recall service fix which includes disconnecting a brake component and the service depts are not connecting it back. At this point, no one knows.
But what my post about how the Prius brakes work shows is that they have redundant mechanical brakes just like any other car manufactured for sale in the USA since 1968, and if the electronic braking system computer has a problem, the computer is bypassed and the car is stopped.
I think it fair to say the brake system is still being controlled by an intermediary compute engine, not directly from the application of pressure on a brake pedal. This doesn't rule out a software issue potentially at root cause does it? Whos to know exactly the failure mode of the system being described through anecdotal reports?
If there is a brake control problem, the computer control is bypassed and the brakes will work.
and what system would determine there is a brake control problem?
COMPUTER CONTROLLED BRAKES STILL WORK if the computer control fails - any other scenario is ILLEGAL.
if these systems were defect-free, then the "trust" could be appropriately placed with the technology. the problem is, these systems are so complex, and the usage scenarios so unconstrained, that there are bound to be failures not invisioned by designers. why do manufacturers issue patches?
scared may be a rather strong word to use. being vigilant, somewhat skeptical, and ultimately a "late-adopter" of technological automation advances isn't being completely unreasonable, and has it's benefits.
crying wolf is not reasonable either of course.
"COMPUTER CONTROLLED BRAKES STILL WORK if the computer control fails - any other scenario is ILLEGAL. "
Actually that is not correct!. Think about it, if the computer control fails, then the computer control cannot handle the brakes.
Yes, there is a failsafe if the "computer control" fails but that is not the computer control system. Er it is a redundant hydrallic mechanical system. Ihe redundant backup systeme works if the computer controlled brakes fail, because the computer controlled brakes have failed. You see ,if they fail they can no longer work.
Branch to *,
MidCow
What I'm saying is that EVEN if EVERY COMPUTER on any car fails, as long as the BRAKE SYSTEM ITSELF does not fail, the car can be stopped.
Brake failures are that - BRAKE COMPONENTS which will not stop the car.
That has NOTHING to do with ANY kind of software based control system.
if these systems were defect-free, then the "trust" could be appropriately placed with the technology. the problem is, these systems are so complex, and the usage scenarios so unconstrained, that there are bound to be failures not invisioned by designers. why do manufacturers issue patches?
scared may be a rather strong word to use. being vigilant, somewhat skeptical, and ultimately a "late-adopter" of technological automation advances isn't being completely unreasonable, and has it's benefits.
crying wolf is not reasonable either of course"
Being a computer programmer who has worked on embedded systems (though not brakes), you must be made aware that these systems are put through all sorts of testing and QA/QC procedures to make sure that things work as they are expected to work. There are very many safety regulations that must be met, and the very fact that the Prius is sold here in the States is a testament that these have been met.
Of course, things happen, and the occasional mistake is missed. But this happens to 'regular cars' as well as hybrids; just look at the recall list. One of the many possibilities of failure for the Prius brakes has to do with the many different possible situations in which brakes are used. For manual brakes, it is simple. But when a computer programmer is given a similar situation, adding on the regenerative braking, things get quite complex.
However, I DO understand hydraulic brake systems and reading the responses I do have a concern: "If there were a serious brake control problem, two solenoids open, by-passing the dead end chamber and computer control, allowing the brake system to function just like a conventional system." Solenoids are electrically driven and something has to activate them to open. A computer or a sensor would be required to send that signal. In a normal hydraulic brake system, the brakes are a closed loop of hydraulic tubes and cylinders that work even if the car is not running and the battery is removed. But if this car has a system that requires the operation of a solenoid to default to the hydraulic brakes in a panic stop, there is a weak link in the system.
Think of the Challenger disaster. No one suspected the O-rings on the booster rockets until they caused an accident.
It sounds like a few people have had similar experiences, but I am still not getting a very extensive feel for how big of issue this is.
"Being a computer programmer who has worked on .."Then just think of Gate's Windows XP with over a million lines of code. Not all million lines were tested for every possible situation. Fuzzy Logic,heuristics, most likely scenarios, etc. are used but rarely is there time to test all possible cases.
" these systems are put through all sorts of testing and QA/QC ... and the very fact that the Prius is sold here in the States is a testament that these have been met. " LOL, don't believe everything you hear. Ever wonder why TSBs are issued ??
Cheers,
MidCow
Cars are not put on the road in the USA which can have a computer failure which leads to brake failure being a systemic problem with the brake design. Redundant mechanical brakes are MANDATORY.
This is 2005, not 1935. There have been hundreds of thousands of Toyota vehicles with this brake system put on the road in the last few years. It's not going to "all of a sudden "start popping up as a DESIGN PROBLEM.
It might be a BRAKE SYSTEM PROBLEM that affects a few cars, but it will not turn out to be a systemic problem, or it would have happened in the Estima minivans which had this brake system BEFORE the Prius.....
Tell you what: If this brake thing turns out to be a software glitch (and is proven to be so) I will renounce my membership on Edmunds Forums and you guys will never hear from me again. That's how confident I am that this is not a software problem. Software is not allowed by U.S. law to control brake systems and allow them to fail because of software failure.
Think "Fail Safe" That means if it fails then it reverts to a safe condition.
Assuming that there are actually two solenoids and they were for a critical redundant, back-up brake system. Then they would be energized in the normal state and would release when the system failed and there was no power.
I am not saying the whole "dead end-ed chamber with computer control to make it function like a normal brake hydrallic system" is not true. But (1) I hadn't heard about it before though interesting concept and (2) it seems like and expensive complex way just to fool the driver into thinking he is driving a hydrallic brake car. Where possible, most design engineers use the KISS method and this just doesn't sound like the solution that would come from KISS principles. It keeps development cost, support cost and system weight down.
Cheers 4-wheel disc,
MidCow
Win XP? Now there is an operating system that has some serious internal problems! Fortunately for most, these arent evident, so it looks fine. But in certain cases, some software that has been written to run in XP will not run!
" these systems are put through all sorts of testing and QA/QC ... and the very fact that the Prius is sold here in the States is a testament that these have been met. " LOL, don't believe everything you hear. Ever wonder why TSBs are issued ??
Having done QA/QC...uh, yeah! In any case, in testing, one tests the heck out of key components, such as brakes. No doubt the braking system has had much more testing than usual. Still, problems do pop up when parts fail unexpectedly... :shades:
Hey, good job! You proved my point. The Prius brakes are under control of the brake computer and we all know what computers run on don't we? Yep - SOFTWARE. Thanks, lars.
As to the likelyhood that there is a perfect fail-safe solution to ANY mechanical system, it depends on how strongly you believe in Chaos Theory: There is at least one random set of circumstances that will void any assumed condition.
Let's face it: the consumer is the ultimate testing lab for any new product. My Prius is an '04, and although I assume that most of the systems had been tested on the Prius Classic and other cars, I am also sure that there are unique combinations of hardware and technology on this car. All I want to do is make sure that there aren't others out there who have had the same thing happen.
So far on this board I've counted 3 different vehicles having this issue. (4 depending on the correct translation of message number 565)
I agree with midcow that the only sane way to design the circuit for those 2 solenoids would be for them to open if the signal is lost, thus assuring hydraulic braking under no power/no signal conditions.
larsb-"Despite it's technological advancements in the way of computerized hybridization for the goal of achieving high mileage, the Prius is in many ways JUST LIKE ANY OTHER CAR including the redundant mechanical brake system."
Actually, no it's NOT like any other car. I agree that the Prius meets specs for a redundant mechanical braking system - but ONLY IF the solenoids open the hydraulic valves, which they should when there is a "serious brake control problem" and "computer control ... is bypassed." So far so good.
BUT
If the 3 or 4 people reporting this brake issue are to be believed, or even if we believe only ONE of them then we must agree that SOMETHING caused the brake pedal to go to the floor and no braking action resulted. Not even 'fo' could disagree with this, correct? So what caused that to happen? Obviously I DON'T know. Perhaps not so obviously, neither do larsb or 'fo'. Here are some possibilities I can think of offhand:
* The car was so poorly maintained that there was little to no hydraulic fluid in the reservoirs.
* There was a serious brake control issue and the solenoids opened but the hydraulic path to the calipers was somehow open - perhaps a bleed plug or something is different in the path via the solenoids vs the path via the brake control system.
* There was a serious brake control problem, perhaps the pedal sensor(s), causing the dead-end pedal system to not switch to the hard spring and the driver pushed REALLY hard and the pedal felt like it went to the floor and the same failure caused the brake control computer to think braking was sufficient.
* The driver suddenly released the pedal and jammed the brakes just as the AC compressor clutch was activated and caused a power glitch and the software missed an interrupt that was supposed to be picked up when the accelerator was released or the brake pressed causing an indeterminate state to be reached in a S/W state machine and ...
Who knows. One thing's for sure - WE DON'T and saying what larsb says in the next paragraph re the HSD computer(s)is totally illogical and irresponsible.
more larsb: "Now, with all that said, there very well may be a SEPARATE brake problem on certain Priuses, but it's darn sure NOT because of the HSD computer.
There may be a part of the software problem recall service fix which includes disconnecting a brake component and the service depts are not connecting it back. At this point, no one knows."
I agree with your second paragraph as a possible explanation, but if that were the case it would say to me that the braking system IS somehow tied into the software problem recall fix therefore indicating the brake system is in the control loop of the HSD(s) - which it most probably IS in some fashion if only as feedback of braking operation. So you may wish to drop this argument lars.
Finally I observe that there are a few engineers talking about this issue and unless I badly misinterpret what they're saying, they ALL agree that it is POSSIBLE that a software error could be responsible for this braking problem. Next I speculate that larsb is NOT an engineer based on his illogic, eg:
larsb: "The Prius brake system is used in the Estima hybrid in Japan. So it was not new.
So my guess from that information is that by now, as a system, it's more than likely problem-free, or they would not have used in in a second vehicle."
Hmmm ... so carrying this logic further, NO brake system can fail because they've been tested and installed in other cars prior to this one.
or
larsb: "If there is a brake control problem, the computer control is bypassed and the brakes will work."
HAHA. NO engineer would ever make a statement like that. Because we all know about the final law of engineering as written by the wrold famous engineer, Mr Murphy: "If something can go wrong, it WILL go wrong."
Witness one of the finest engineering marvels of the recent past - the Space Shuttle. 2 of them lost to unbelieveably simple stupid mistakes. Murphy lives.
Oh and, BTW, to head off 'fo' or larsb saying 'well they weren't brought down by software problems' I'll add right now that there are FIVE computers on a space shuttle ALL running the same software and FOUR out of the FIVE must agree or a major malfunction alert occurs. How many computers on the Prius must agree before the level of braking is determined?
Like I said before, I'm staking my good reputation at Edmunds and my enjoyment of posting here on the fact that the supposed brake problem will NEVER come down to having been a "software" problem. Modern cars just dont have software problems that lead to brake failure, not after millions and millions of Prius miles worldwide and millions of Estima miles before it.
Time will tell......:D
one controls engineer's vote for the possibility that SW is still involved with the failure based on the description of what was posted.
i could also see, for example, the possibility that there was a low-tech problem, air in the hydraulic lines that wasn't bled out. we don't know for example how the design operates at low-speed, where i presume there'd be little advantage to regenerative braking.
1. If the car's brakes go to the floor and stop working, and it's a BRAKE SYSTEM PROBLEM, then restarting and driving the car again after the first failure will result in subsequent failures EVERY TIME. In other words, the brakes will NOT WORK AGAIN until the brakes are fixed, no matter how many times the car is restarted.
However,
If the cause IS related to a random software glitch IN THE BRAKE SYSTEM not in the HYBRID DRIVE system, then the brakes SHOULD WORK again after restarting the car.
Do any of the owners who have had the brake problem know the answer to this question for THEIR car?
This one was posted earlier and became one of the posts that helped generate the "brake issue - software?" discussion.
This one ABSOLUTELY sounds like an ABS system problem, with the pulsing situation, which would definitely fall out of the "software because it's a hybrid" category COMPLETELY wihtout question.
WHILE DRIVING UNDER NORMAL CONDITIONS, I EXPERIENCED A MAJOR BRAKE MALFUNCTION (BRAKES BARELY RESPONDED AT ALL--ONLY BY PUSHING BRAKE PEDAL TO FLOOR DID I MANAGE TO SLOW DOWN/STOP VEHICLE). A CONTINUOUS WARNING BUZZER SOUNDED, AND THE ABS WARNING LIGHT AND BRAKE WARNING LIGHT REMAINED ILLUMINATED ON DASH. VEHICLE HAD TO BE TOWED TO NEAREST DEALER. THIS COULD HAVE LED TO A CRASH AND INJURIES IF TRAFFIC HAD BEEN HEAVY. I BELIEVE THIS IS A MAJOR SAFETY ISSUE. THE PROBLEM WAS DIAGNOSED AS A "BRAKE ACTUATOR" FAILURE, AND THE PART(S) ARE CURRENTLY ON BACKORDER. THE VEHICLE IS A 2004 TOYOTA PRIUS.
FLUID ON LEFT REAR TIRE RIM AND LOSS OF HUB CAP. DISCOVERED LEAKING BRAKE CYLINDER ASSEMBLY AND SOAKED DISK BRAKE PADS. MASTER CYLINDER BRAKE LEVEL DOWN TO TO MINIMUM FILL LEVEL. BRAKE FLUID POOLING ON GARAGE FLOOR UNDER LEFT REAR WHEEL. *AK
2005 Prius software glitch:
DT: THE CONTACT STATES WHILE STOPPING, THE BRAKES RELEASED. THE PARKING BRAKE WAS USED TO STOP THE VEHICLE. THE VEHICLE WAS TAKEN TO THE DEALERSHIP, BUT THEY COULD NOT DUPLICATE THE PROBLEM. THERE HAVE BEEN NO REPAIRS MADE AT THIS TIME.
Software or hardware? inconclusive without more reports.
actually, if it were a SW problem, it is quite reasonable that a vehicle start cycle would clear / reset the conditions leading up to a problem like this.
you would not find support amongst engineers and specifically programmers that a system failure means that there will be subsequent failures "EVERY TIME"...
every time what?
such is the nature of complex systems and embedded controls.
That's why your brakes will still stop your car EVEN IF THE CAR IS OFF. It will stop SLOWER, but it WILL STOP.
I called my dealership and was given a toll free number for people with my problem (scary that it exists--but helpful). They called a tow truck for me and offered to call the police.
Now I am just waiting. Does anyone know how long this takes to fix?
"This one ABSOLUTELY sounds like an ABS system problem, with the pulsing situation, which would definitely fall out of the "software because it's a hybrid" category COMPLETELY wihtout question. "
Are you sure the grammar was correct or did you mean to say:
"This one ABSOLUTELY sounds like an a BS system problem, with the pulsing situation, which would definitely fall out of the "software because it's a hybrid" category COMPLETELY without question.
Couldn't resist :P
Cheers,
MidCow
I feel you pain. I was driving my 79 Toronado home one night and the dash lit and it coasted to a stop. The power brakes failed, the power steering failed and I barely had any braking or steering left at all. It would not start and I had to have it towed. ASnd to top it off i had to walk to a service station because I didn't have cell phone or Blackberry. It was a failure of the computer control module. They replaced and nary another failure.
I just could not believe it the car was only a year old. So I decided right then and there that all cars were bad and I would never drive again. They were just too complex and unreliable.
Luckily I changed my mind :confuse:
Cheers,
MidCow
P.S.- Falconone -- you are not really cancelling your Prius order because of the braking discussion are you ??
I agree that the only sane way to design the solenoids would be for them to open upon the loss of signal. But what if there were a set of conditions that tricked the computer into thinking that the car was stopping under regen and the signal wasn't lost? I think the accident unfolded something like this: My wife was in city street traffic, fairly heavy, and had let a large SUV into the flow of traffic about a block before. Traffic was starting and stopping, probably never exceeding 20mph, but she does not have a recollection of looking at the speedometer. She was maintaining a following distance of approx. 2 car lengths. At some point, the SUV stopped, and she started applying the brakes. Because of the nature of the traffic flow, I suspect that it was a fairly weak pedal pressure. The brake pedal "pulsed" several times, but not the rapid ABS type of pulse, but a slower on-and-off feeling. She then applied harder pressure to the pedal, but the car didn't stop. She thinks the pedal went to the floor but can not be positive. I suspect that the time lag between pushing harder and hitting the SUV was about 1-2 seconds. After impact, the car was not running and all of the warning lights were lit, but she doesn't know if it stalled before the accident or as a result of it. The car restarted and she pulled to the side of the road and the brakes worked. After exchanging info, she drove 1/2 mi home and the brakes worked.
She told me that the car had done something similar 2 or 3 days earlier while backing out of the driveway (pulsed), but the brakes stopped the car and after shifting into drive they worked normally.
From what I've read on this site, it sounds like the car's speed was just slightly above the automatic hydraulics-only speed of 7-8 mph. And with light brake pedal pressure, the computer could have been in a normal regen braking mode. Is it conceivable that there is some combination of speed, brake pressure and crossing over the auto threshold that could cause a false-positive signal from the computer, even for a second or two? Let's face it, I would guess that the deceleration from 10 to 0 mph was rather abrupt. Also, does anyone reading this know what the normal status of those solenoids is? Normally open or normally closed?
Also, the pulsing feeling could have been the normally slight 2-3 time lurch that is felt as the ICE disengages. It could have felt that way under the circumstances.
Cars should be able to stop even when turned OFF, including the Prius.
I want to jump in here quickly before 'fo' finds this and blames the accident on his nemisis - the large SUV (probably a Navigator) in front of your wife. Get all the large SUVs off the road and that one would not have been there and 'voila' problem solved.
And, of course, larsb is sticking to his story.
I read this and I wonder if it does have to do with the stalling issue - you do say that the car stalled either before or after. If it happened before or was in the process of stalling that could have caused the brake system to be 'confused'. I haven't read whether other folks have trouble stopping their Prius when it stalls. I wonder ... though the stalling seems to 'stick' in that the stories I've read say people have to have their cars towed after they stall. So perhaps it wasn't that at all.
Your hypothesis about false-positive is something to think about.
In any case, she said it had done something similar a couple days earlier. This sounds pretty serious for you guys. I would certainly stay right on top of the dealer and perhaps Toyota hotline and make SURE they find and fix this problem. Might be a good idea to add this to the NHTSA database as well. Don't know if you've looked or are aware, but there are other reports of similar issues with the Prius. Good luck.
Get a deserted road, preferably a long private driveway.
Get your car going up to about 15 mph.
Put the car in neutral and turn it off.
Apply the brakes.
You see how the car stops, slower but surely? That's how it will stop if the car stops working or stalls. Brake systems stop cars without power assist.
So Prius owners - if you're afraid your car won't stop - just turn the darn thing off! That'll take the software out of the loop!! HAHAHA LOL as 'fo' would do.
Everyone is getting into "trying to prove something" mode, and we're going around in circles. Time to ease off before the little shots start to turn into insults.