NHTSA Tracking Braking Loss on Prius Hybrids

Efusco,

"vendetta" is such a strong word! I think the OP was done a disservice by his dealer in that they should have continued to work with him and then escalated the situation to TMC if they could not resolve the situation...and the dealer should have offered a buyback if nothing else worked as a last resort. I personally don't think it's warranted asking for a refund on the car purchase- I certainly would not have gone that route- but I don't think he's got a vendetta going..."I don't think there is, but perhaps I'm wrong"!!!!

At any rate, I don't blame a person if he exhausted all his options and still got nowhere with his dealer or TMC and then went to greater lengths to get his story out there. I'm just hoping that TMC takes these threads into consideration and looks into the matter. I don't think it's a safety issue for you or me. We're aware of it and we know what's happening when it happens. When it happened to me if I had panicked and taken my foot off the brake and plunged it down on the other pedal I would have run over my mailbox and trashcans and would have done only very minor cosmetic damage to my car. Others may not fare as well and it MAY be a safety issue for them.

If TMC looks into it and decides that the chances of anyone every doing the "rapid foot pedal switch" trick when this loss of brake sensation happens are non-existant and that everything's fine the way it is, then so be it. Still, it deserves an investigation and at the VERY least a warning be put in the Owner's Manual, and bulletins issued to dealers telling their salesperson to very carefully explain the situation to potential buyers...(not exactly a great sales pitch though!)

I'm going to enjoy my Prius either way.

 

Dang, Bighouse! You just explained a nagging question that I've had for years: how do people drive their cars through store fronts and then claim that they "thought they were stepping on the brake" when they were really stepping on the gas! It was the ol' "rapid foot pedal switcheroo" maneuver!

 

Actually yardman, it happens! I just gave it a name.

Honestly, I think a lot of these kinds of things are user error. BUT, good systems take into account stupidity especially where the safety and welfare of people are involved. I'm an architect. There are a TON of codes out there which, for 99% of the adult people in the world, wouldn't create a hazardous situation. BUT, it's the 1% who will put their foot on the gas instead of the brake when the brake pedal doesn't do what they think it will (perhaps because it's got a floor mat under it???) that cause the issues to become safety ones. Codes and regulations aren't there for those who don't need them.

 

I'm trying to resist the bait. You have made your point, but others may not agree. I don't. I have already stated my opinion. I've driven my car over 33k miles at this point. Other Prius owners have logged hundreds of thousands of miles. It is a known issue, but I don't consider it to be a safety issue.

When you want to brake, you push the brake pedal, no different than any other vehicle. If you take it off the brake and push "the other pedal" it will accelerate just like any other vehicle. So you want to investigate an issue because you think that "others" MAY have a problem where they may push the wrong pedal? That does not seem to be an effective use of NHTSA resourses.

 

Well not quite. At times, if you push the brake pedal and happen to hit an uneven surface of the road, it's quite different from other vehicles. In all other vehicles I've ever owned, including those with ABS, the brakes continue to work even with the influence of potholes...

I'm actually growing weary of the debate/discussion. I just hope I don't have to say "I told you so" when/if any accidents happen from users who panic and don't do the right thing when the brake-loss happens to them. I'm actually hoping, also, that TMC looks into it and makes voluntary adjustments so users won't be wary to purchase a Prius based on this initially scary event.

 

You have my permission to start a "told you so" thread when there is a verifiable accident caused because someone in a Prius lost regenerative braking for a split second while the car switched over to friction braking. Please try to limit the thread to less than 13 pages. :madgrin:

 

OK I went out again today and tried to get my 2010 to do this. My 2007 would do it much easier then my 2010. When I tried yesterday, I could not get it to do it. I was more determined today. I tried manhole covers, potholes, construction areas and could not get it to do it at all. I finally went to a parking lot with the speed bumps and was able to get it to do it on a speed bump once. I tried several times (over 10 times) and got it to do it once. I normally do not negotiate these speed bumbs this fast.

Here is what my car does and it takes a severe bump or obstruction to do it in my car. Upon going over the bump, there is a momentary (I mean momentary as in a fraction of a second) loss of braking and the brake pedal losses pressure. Now I am ready for this, so I held the brake pedal steady. I did nothing, so after a fraction of a second, braking resumed and I estimate no (none, zip, nada) loss in braking distance, as it happens that fast. What I suspect is happening is that the feel of the brake pedal is causing a let off reaction similiar to the ABS reactions that happened when ABS first came out. For those of you who have or are experiencing this, please try to document your experience as I have and please post your results also.

Conditions.
Speed: 20 MPH
Terrain: Paved Asphalt Dry
Obstuction: Parking lot speed bump aprox. 3-4 inches in height

 

Hello BMM:

Did you notice if the "traction" warning light came on (even very briefly) when this happened? In my 2009 manual, it says that the TC light can come on when the ABS is working. Also, ABS activation can cause a loss of pedal pressure according to the manual.

 

I do have to comment on this subject yet again. I used to own a 2007 Honda Civic Hybrid and the discussion with the Prius used to happen to me (Frequently) in the 2007 Honda Civic.

Repeated service deparment visits, returned that it was the ABS system working as designed. There were no flaws, no repairs, and although I experienced it often it had become second nature to me once I knew it was not a defect.

I have only had one occurence of this in the 2010 -V model. Negligable in my opinion. Maybe it was because I was so used to it, I didn't make anything of it.

As in the 2007 Honda Civic, the first few times, were "eye-opening" so once it became something I was familiar with, I was not shocked by the recurrence later on.

So maybe this is just a learning curve to those who never had this type of experience and find it a little unsettling....

I hope as well, there is no issue, but I suspect it's normal operation, since it's "identical" to the Honda experience.

 

hahaha! I'm hoping such a thread never exists!

 

I decided to go grab my 2009 G2 manual and look up some info. On page 167, I find this:

Any of the following conditions may occur when the above systems (ABS, Brake Assist, VSC, EPS) are operating. None of these indicates that a malfunction has occured:
- Vibrations may be felt through the vehicle body and steering.
- A motor sound may be heard after the vehicle comes to a stop.
- The brake pedal may pulsate slightly after the ABS is activated.
- The brake pedal my move down slightly after the ABS is activated.

The brake "moving down" seems to be part of this phenomenon as described by those such as the OP who seem to be expressing the most concern. This would be indicative of the ABS activating.

I'm wondering now if possibly this braking issue is actually more severe on some Priuses than others?? Most of us we have either never experienced it, or only rarely experienced it; and then we learn what to expect and move on. But could some Priuses actually have a "real" issue where something is out of adjustment, alignment, or whatever, and it is causing the problem to occur more frequently and/or more severely??

Just wondering here........

 

I just wanted to throw a few things out there:

1. The brake pedal "feel" is simulated and has no relation to what is happening with the wheels or braking. So the pedal won't "go to mush" or "fall to the floor" as your foot is not acting upon any system other than a brake pedal stroke simulator and a position sensor. This is why you can easily push it all the way to the floor to enable the hill assist. If you were in a normal car without brake-by-wire and the pedal goes to the floor, be very scared.

2. It's been determined this "problem" doesn't affect maximum braking, and if you quickly push the brake pedal on a Gen III, you will engage Emergency Brake Assist. Give it a try with a quick but not maximum effort jab and the car will apply max braking pressure as if you had slammed it down. You have to let off a lot before it releases max pressure. If you were slowing down with regen and experienced this problem, all it would take is a quick push to engage the brake assist and you will come to a VERY quick stop.

3. I haven't experienced this on my Gen III and roads in LA are very bumpy -- but I also don't make it a habit of braking over bumps as this quite hard on the car. (Also, on my motorcycle it could spell disaster.) Of course, sometimes I have to brake over bumps but when I do it, I'll probably be stopping rather quickly and the friction brakes will already be engaged so this will never happen....

4. Like many people pointed out, identical arguments came out when ABS was released because people weren't used to them. Regen brakes need to be learned as well. In addition, I bet we heard people saying stuff like: "The traction control cut power because the tires slipped and I almost got hit by a truck! It's dangerous."

5. It is understood that when humans get panicked, it feels like time was slowed down. If the braking cuts out unexpectedly and you get freaked out, it could feel like it was doing it for "2 or 3 seconds" but in reality it is probably just a fraction of a second. Someone needs to take a G-meter into their car to datalog this happening. You could then very accurately measure the time and amount of brake loss.

6. I feel the braking system works very well on the Gen III, and I don't want some mandate coming down to reduce or eliminate regen braking because people can't get used to driving it. That would certainly lower FE. I hope the only "FIX" that comes out of this is a letter to Prius owners telling them about this behavior and a change in the owners manual.

Thanks for listening.

And one question, can someone replicate this and look at the HSI to see if the regen indicator goes away?

 

I know, I'm just adding to the voices in the choir here. I own a Gen III, Prius IV. I have a 2010 Prius. I’ve experienced this problem about half a dozen times while decelerating / braking. When the car hits a bump, it feels like the braking pressure goes to 0, which gives me the sensation of the car lurching forward. I’d imagine the chance of something catastrophic happening are probably pretty low, but this is probably a legit safety issue rather than a performance characteristic of the car (a bug, not a feature, right?).

I'd be curious to see where this goes, if anywhere. And to answer an earlier question, I'd totally buy my car all over again if I had the choice to make again. I just want this issue investigated.

 

One has to love forums, and the mention of another thread A perfect storm of doubt has epitomized the sometimes silliness of it all.
Now the poster of the particular thread has been a member for 7 months, and managed to post 470 times!!! on a vehicle he admittedly does not own.
I also belong to Ferrari chat and have so far twenty or so posts and I own the car!.
So far I have zero problems with the car, and I think most of us are in with me on this.

 

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470 times? Wow, someone must be really living up their xmas break!

I love my car, I only have the minor braking concern, but I wouldn't trade it for anything else in the world. Okay... not true, a tesla roadster would be nice.

 

Kiet Do,

While I appreciate the invite, I would rather not participate in the story at this time. I feel the verdict is still out to some extent as I want to wait until Toyota Motor Corporation chimes in on the matter. I would ask that you keep me in mind though and after I've seen some feedback from Toyota I might be willing to help you out in an interview.

(Well gang, I told you it wouldn't be long before you heard it on your local news...I sure hope TMC steps up to the plate and releases some info soon before the story goes nationwide.)

 

I'm in this group. I've driven 137,000+ miles on my 05 with no issues whatsoever. I recognize the characteristic of the vehicle but I've filed it somewhere about 2000 or 3000 issues deep on things that I have to be aware of on a daily basis.

Over the last 8 yrs I've driven and been passenger in maybe 2000 different Prius'. Not a single person has ever mentioned this characteristic - ever. I worry more about what might happen in the year 2012 than this characteristic of the Prius...which means NEVER.

Why would it be that the 'more experienced' group of drivers think this is a non-issue while the first-timers run to the Feds? This is the most surprising issue for me.

 

On our recent Christmas Eve, a warm night of 40 degrees F, with my teens in tow, I drove as usual to the end of our street at about 15 to 20 miles per hour in my 2006 Toyota Highlander Hybrid. As I approached the stop sign, and before the busy cross street ahead, I gently pressed on my brakes, slowing even more to about 10 mph and then further. However, instead of the HH brakes fully engaging as desired and typical at the stop sign, the car then "surged" forward for a brief period of time, heading directly towards a 35 mph car traveling on the cross street. The teens yelled, I press the brake harder and the car stopped abruptly, to our collective "wow" and "thank goodness".

There was no ice, no wetness on the street, no pothole or bump, no let up by me on the brakes, no improper tire pressure, no used or improper brake pads (just had that checked at 35K check). Just failure of the HH to brake when needed, and strong sensation of forward movement for a brief time (seconds) when critical. And unneeded alarm, as this was not the first time in my HH that I have encountered this brake surge, nor will it be the last time. I will once again report it to our dealer, as I have since the car's purchase. Toyota needs to address this serious problem.