NHTSA Tracking Braking Loss on Prius Hybrids

I have filed a complaint with the NHTSA as I have experienced this and believe it is a serious concern. I tried to recreate it today and was easily able to right near my home. Again, I do not get the pulsing when this occurs but simply a feeling of being on the worst ice patch possible and just sliding.

Tom, that's an interesting note about your ABS. If I brake hard on snow or ice, I definitely get the pulsing, exactly like my Odyssey does. Have you driven a 2010 yet? I may be up in your neck of the woods in the next couple months and would be happy to let you do a test drive in mine.

 

I experience this problem as well. On my daily commute, a sharp right turn on a bumpy patch will cause the car to surge forward requiring additional brake pressure. I now have to decelerate on the main road before turning or the problem is easily triggered.

 

This happens with both my hybrids while braking and hitting a larger than usual pothole. A little more pronounced in the Prius...I always seem to say out loud, 'Whoa' when it happens. Feels like the car picks up momentum.

 

It's not picking up momentum and it is not a problem. It's because all of your braking is coming exclusively from your regenerative brakes, which are exclusively the front wheels. I've noticed that this car lurches forward moreso than others because of that. (Understandable.) When you loose the traction due to the pothole, and in that milisecond that it takes for the friction brakes to kick in, the car may seem to lift in the front, kind of like during acceleration. It's very deceptive.

This is just going to waste a lot of money, and the only end result would be a car that is less efficient. I've seen some of you had 2nd gens, but are most of the people complaining new to regenerative braking?

 

I agree, it doesn't really accelerate, its your senses tricking you. When you press on the brakes, you involuntarily make adjustments with your body to counteract the deceleration. When you don't encounter the deceleration, you think the opposite is happening. Try this, while you're driving, put your car in neutral and press the gas pedal, you'll find your head tilts forward in anticipation of going forward. Same thing with the brakes.

 

I don't know of any reports of the FFH doing this. The FFH has had a few instances of regenerative braking failure under normal braking with associated warning lights illuminating and much larger pedal movement required. Turning the car off then on restores normal function. There is a TSB wiring harness modification for vehicles that experience this. This is a flat out momentary regen braking failure thought to be caused by a connector. The Prius problem sounds like software.

 

I believe this to be the case. The complainers are mostly ( all? ) new hybrid owners, new Prius owners with new Gen 3's. In addition to my own Gen 2 I've driven about 100+ Gen 3s with no noticable difference between the two in this regard.

 

I've never felt the pulsing of the anti-lock brakes, even on icy surfaces when I skidded on purpose. (Was out testing the traction control, etc, in the recent snow.) As far as I can tell, the anti-lock brakes give no indication -- either in the pedal or via noise under the hood -- that they're working.

That would be my theory as to at least some of what's happening: anti-lock brakes are kicking in silently under conditions where you're not expecting them, disorienting people. I've driven 6600 miles so far in the city and on interstates and haven't once experienced something that jolted me. Not saying it can't happen tomorrow, but...

 

I've had this happen to me a couple of times as well, but I've not been panicked over it because I'm used to driving older cars with bad brakes. The brakes on the 1994 Blazer my 2010 replaced were worse than that even on a good day.

 

Thanks for that feed back, W. There was one member who reported that they felt the ABS pulsing. But most have not.

Possibly the degree of pulsing is modulated such that at lower braking pressures (pedal pressure combined with tire traction) it is not discernable, whereas it is at higher pressures it is?

If so, then the "loss of braking" may indeed be due to the switch over "to friction with ABS", not just the switchover to friction alone.

 

It's not a "problem" until it's a problem. It doesn't matter whether it's an issue with the ABS (which I feel it is not) or whether it's a software issue in the transition from regenerative to friction braking (which it may be).

Many posters/repliers here seem to be in some kind of major denial camp..."oh, it's just the way the technology works...oh, it's just people who aren't use to driving a hybrid...etc" but I have read some posts from a few here who, after having experienced it for the first time, have made clear statements that they too were a bit shocked and slightly terrified when it happened. People panic when they try to bring their car to a stop and suddenly the brake pedal goes to mush. It's very unsettling and it is NOT expected behavior for a system (i.e. BRAKING) that everyone has used for years and expects to work as it has in the past (i.e. put your foot on a brake pedal and you come to a stop) does not work.

I'm willing to bet Toyota will be hit by a lawsuit in the near future if this issue isn't addressed. Given the observations/shock/panic/fear/concern/dismay of many of us who've experienced it I am quite certain that it WILL be a problem when someone can't stop at a signal because they hit a pothole a tenth of a second before the crosswalk and ...and instead of continuially depressing the brake pedal until it kicks in, they switch pedals to apply pressure to the "other brake"...and someone gets hurt.

So, while it may not be much of a problem for most of us, it will be a tragic problem for one or two people...and when that happens it'll be a HUGE problem for Toyota.

I can hear the news now..."Could these deaths have been avoided? Internet evidence shows Priuschat users make brake failure observations/posts LONG before Toyota admits to problem"....

FWIW, I love my Prius. I'd keep it even if this was a problem Toyota can't solve. But, I'd have a lot more respect for the company and trust in their products and hope for the longevity of the automobile manufacturer if they did the right thing about this and other issues of quality control.

 

There are over 1,500,000 owners, most of whom are in denial?

The shock of sliding on hidden ice is far more dramatic and happens much more often. Yet, that's accepted as a norm across a wide range of vehicles. We've also seen the opposite extreme when new owners panic from seeing the battery get low.

What exactly would this lawsuit be for?
.

 

Not knowing how to drive and or panic over this is not Toyota's fault. If you are unable to function and or panic when this happens, you may want to consider turning in your drivers license so the rest of us who can handle this are not put in danger by your panic attacks.

 

Here's what it will be for...Negligence: "Law. the failure to exercise that degree of care that, in the circumstances, the law requires for the protection of other persons or those interests of other persons that may be injuriously affected by the want of such care."

It will be for someone saying that their brakes failed on them and so they switched to the other pedal thinking they must have used the wrong pedal when this issue was so widely discussed on the internet, brought to Toyota's attention by Prius owners and even published in magazines/journals and articles.

Sliding on hidden ice in cold weather when snow and ice are a possibility is expected. Pressing on your brake pedal and having it drop to mush isn't. Ice has been on the roads for years and people understand that. Having your brakes go from slowing you to having them appear non-existant in a heartbeat isn't expected or within the normal range of driving expectations. The two are not even comparable.

 

bestmapman,

You're missing the point. One should NEVER have to have this happen! It's a fault in design. Plain and simple. It should NEVER happen. One should not have to AVOID a panic situation brought on by a system that puts one in a potential panic situation given otherwise a totally non-panic conditions.

I'll put my driving record and ability to handle a panic situation up against anyone. My driving ability isn't what I'm concerned about. It's the driving ability of others...I'm sure you're an excellent driver as well and won't ever have an incident caused by this issue- however, others on the road are not as capable as you or I.

Believe it or not, I'm trying to HELP Toyota and Prius owners...not bash Toyota or the Prius...or Prius drivers. I don't know why so many of us are so quick to defend Toyota in what seems to be a pretty obvious case of "they really should find out what's going on here and fix it before someone gets hurt".

 

Lets get something straight. It just doesn't happen out of the blue, it happens when an obstruciton of bumb is encountered. So, having the brake pedal mementarily change it's function as related to the regenetive braking is something that you need to be aware of. Again it is during "light" braking. If you were in heavy braking and the friction brakes will be engaged and you should not feel the same reaction.

It is during "light" braking is when this is happening. Therefore it is not an issue of stopping distance, it is an issue of driver knowlege and skill.

It is your opinion that it should never happen. I have it happen every so often and am used to it. It is expected when going over a bump. The HSD is a different transmission then a standard automatic or standard transmission. In those transmissions the brakes are independent. In the HSD, regenetive braking is part of the transmission process. This is a normal function and I think when you get used to it, you expect it. People should be made aware of it and master it. If it was eliminated fine, but I don't think it is a problem from my perspective.

 

And, again, from my perspective it's not a problem for ME or YOU.

It WILL be a problem for others when an accident or accidents start happening. And so regarding the changes/adjustments one must seem to make as a hybrid driver and, borrowing from your own words, that's your opinion- which when someone else gets in an accident and it's caused by this issue, won't amount to anything.

I agree with you- adjustments must be made, but when it comes to some issues, like the sudden loss of braking, that's a MAJOR safety issue that should NOT have to be compensated by a driver's ability. In the end your opinion/perspective doesn't matter- nor will my opinion.

Only facts and lawyer arguments will matter then...

 

Well I think you hit the nail on the head.

 

Better understanding.

Setting of expectations.

The abrupt jolt of the downshift when accelerating hard from a traditional vehicles can scare the crap out of a new automatic-transmission driver too.

For ice & snow and even rain, the tires make a huge difference. Yet, there still is no real standard for factory traction.

How is this different?
.