Arbitration With Toyota (2010 Prius V, problems with breaks/acceleration))

Cars have brakes. When they break - they stay broken until fixed.

 

1. It's the normal regenerative to friction braking transition that you're experiencing. The car doesn't actually accelerate but feels like it.

2. Do you have the V (Five) with Advanced Technology package? If so, either the PCS (Pre-Collision System) has triggered or you had the adaptive cruise control on and it slowed down on purpose. This is normal.

Educate yourself on these issues before you lose the arbitration (which you will anyway as they're normal behavior).

 

Priuschat used to be a good forum, but apparently the jerks have taken over! If you can't help the lady, please excuse yourself.

 

It used to be worse before the brake campaign was initiated (the regenerative to friction braking transition was previously too long for most customers' level of comfort). It's a trick on the brain, but nobody has gotten into an accident from it. Suppose you thought the car was on but it wasn't and you step on the gas pedal, your body naturally moves forward expecting the car to go. Same mind trick.

Someone actually reported the same thing here, but the possibility that an unseen object or debris moved in front of the car couldn't be eliminated (there's a lot you can't see in front of the hood). Was this a one time incident? If so, you have nothing to worry about.

I don't know why they couldn't take the time to educate you properly, but most likely they're also ignorant on the issues and it takes an "expert" to explain the issues.

 

Sell your car.

 

The first issue is normal. The car has small tires and bumps/slick roadways will trigger the regen braking to stop and the abs/friction brake to take over this may feel like the car starts going faster but is only a short period of brake loss.

Second issue i have read about before. I am sure you can have the system disabled then you will not have to worry about the car braking again.

 

This post starts at 11:17 and by 17:25 there appears to be some irritation building that a useful reply has not yet been received. I'm sorry we didn't get back to you soon enough. We're not paid to monitor the chat room & some of us have real jobs.

Spelling is important. OP is initiating legal action, not appearing on Judge Judy. Different words have different meanings & OP has a case to prove.

1. When the "acceleration" while braking was felt did you notice the speedometer increase from say 10mph to 11mph? (My guess is no.) When this sensation was felt was more pressure applied to the brake pedal? If so, did the car stop?

There is a transition between regenerative braking & friction braking. During this transition the car does not continue to slow. The human body expecting a steady rate of deceleration interprets this as acceleration. As OP alludes, this condition is very easy to reproduce. Lightly brake over a storm grate, bumps, holes, a painted section of asphalt (ask a biker how slippery paint is) and this effect will be felt every time.

If this effect is likely to cause a collision then the Prius does not maintain a safe distance.

2. Radar Cruise Control and Pre-Collision System are not designed to bring the car to a stop. RCC will engage the brakes to maintain the set distance. I don't know how slow it will allow the car to get before it hits something as I'll apply the brakes first. In a game of "Chicken" the car will always beat me.

The easiest way to determine if PCS is working is to brake hard. As the OP describes, the seat belt tensioners will pull the slack out of the belts to hold the occupant firmly in the seat. Additional braking force is also applied. The car beeps & some light or lights are lit. I don't know which lights.

On two occasions I have had a deer cross my path within inches of the front bumper. RCC & PCS did not activate. I have not had a phantom activation so I will not speculate on what may cause them.

Did OP's two activations have anything in common? If so, it may be reproducible by returning to the scene.

Question to OP: What is your tire pressure? Since you are complaining about handling I suspect your tire pressure is low. Your 17" tires are rated for 51psi (read the sidewall). Pump them up to max. sidewall. Are the symptoms reduced?

When you were invited to the dealer's New Owner Party did you go? Did you mention these issues? Did one of the employees offer to demonstrate how things work? Did you bring these issues up during the Q&A period in front of everyone?

My credentials: In my signature you can see the number of miles I logged in both cars. The 2010 was bought in the last week of December 2009. Both cars have been driven in rallies and autocross. I took the 2010 through the AAA Advanced Driving Program last year.

I'm not sure Toyota would classify me as a "fanboy". Early in its life I experienced ABS failure in the 2006 on my commute to the office. I turned around and drove past a Toyota dealer to have the selling dealer fix the car. As I remember it took about 4 days for them to fix the car.

Early in its service the 2010 left me stuck in a parking lot one morning when the shifter would not move. After an hour or more of futzing with the thing I worked it free & drove it back to the selling dealer. Nothing was done as the problem could not be reproduced. It has not happened again. You should be able to find my contemporary posts about these issues and see that I was not amused.

In conclusion, you asked for advice. Here's mine.

Check your tire pressure & inflate to max sidewall.

Go back to the troublesome intersections on your route and reproduce the sensation. Look at the speedometer then press harder on the brake.

Enroll in AAA's advanced class. Right now you only think you know how to handle your car.

If this is all the evidence you have drop the case before you waste a lot of time and lose.

If you were in the "area" I would offer a demonstration.

Please return & keep us posted.

 

This was rather difficult to read.

I don't know much about the RCC or PCS and the regenerative brake issues have been covered. So all I will say is I hope that your issue gets resolved quickly and in a satisfactory manner. Sorry, this thread turned out so bad. Best wishes.

 

Well, that isn't normal. Sounds like it might be a defective pre-collision system sensor. You can disable PCS in the meantime. There's a button to disable it if you'll check your owner's manual.

As for the first issue, leave that out of the arbitration process or you'll come across as ignorant of the issue. It's a normal part of regenerative braking. The Gen II has this same regenerative to friction braking transition. Just something to get used to when it comes to hybrids.

 

I experienced #1 in my first drive of a friend's '04 GII back in the fall of '03. He explained what happened (the regen-to-brake thing as a result of hitting a pot hole on the DC beltway ... yes, it *does* feel as though you're accelerating, but you're not, really). Didn't stop me from buying one 2 days later. Or the one that came after that. Or another one week before last.

The most recent one (a v) only has about 400 miles on it and haven't had this experience (yet?), but both previous GII's would occasionally do it (occasionally coinciding with the Tire Slip indicator coming on briefly). It's only unsafe if it causes you to panic. Perfectly safe, mechanically-speaking.

As for #2, I would guess that if PCS is responsible, shouldn't there be some indication in a read out of the black box "thingy" in the car (that dealerships can access?) that either of these 2 things occurred?

Did Toyota actually tell you what they did/their results? If not, my recommendation might be to do a little leg work to find a more sympathetic/customer satisfaction-inclined service center to help you through it and who will explain what they did and what they learned (then share it with us).

Failing that, I agree with LulzChicken that you should consider selling it if you feel it's unsafe. Admire your wish not to want to pass your problem onto someone else, but their experience may very well be different (esp. if Toyota's confirmed they can find nothing wrong). You may be pleasantly surprised how much you get for a used Prius (I certainly was). They really hold their value.

I also kind of agree that it might be good to turn off PCS to see if this doesn't eliminate the problem (per 32kcolors). Sucks that you'd have to disable a feature you paid for, but maybe it's a "feature" that would serve you better if disabled.

Hope this helps.

(fyi, inre #1, found this fascinating ... and don't let the nit police get to you ... it's perfectly clear what you meant, and that's what counts.)

 

It was debated to death !!! It is just a feeling what happens is the deceleration stops for a couple of hundred millisecond. You feel it accelerate but id DOES NOT. It keeps the speed momentarily rather than slowing. The car was too sensitive originally for bumps etc ... so that was the fix BUT the breaking MUST cut over from regen to friction breaks. If I really try I can tell this happening on a very smooth surface around 7-9MPH when this occur as designed. This sensation is stronger at higher speeds and "harder" breaking. It is a real sensation NOT imagined.

Now, if you were right indeed there would have been a lot of accidents from this but there were NOT.

I do not know about you but many years ago when I drove a ABS equipped car and that came on first time many months after I was driving I thought that WAS WRONG ... but it wasn't

You will NOT win on this point.

I do not have any advance package so I can not tell how/if this could happen

Question: was the car breaking really hard?? Were the tires locked up and sliding ?? Did it get out of its path (like skidded right/left) ??? If the answer is no for these then this could be done by a driver as well so nothing really that dangerous was created. A PCS supposed to do exactly this try to stop the care as soon as possible without locking the wheels ... Now, I do see an issue if this could randomly be triggered.

But what are trying to get from Toyota? Are you saying that you stopped using the car since you filed the paper ?

Anyway it is possible that your car is a lemon but I guess for that you need something reproducible problem. You may have been better pursue that avenue (each state is different though)

Good luck ... anyhow ... (maybe just sell it it must be a very low mileage car )

 

Calm down and breathe...

Step #1: Disable the Pre-Collision Detection System. If it is falsely or truly triggering, it won't anymore. What you describe is exactly what is supposed to happen if the PCS detects an imminent collision. Obviously if it falsely detects a collision, then it will do the same thing.

Step #2: Read up on velocity, acceleration, and jerk. Also read up on how the human body has some of the worst sensors. You can prove this to yourself. Buy (or rent) an accelerometer. If you have a smart phone, you can download an application that will show you a graph of acceleration because most phones have accelerometers built in. Then find some place with a pothole, manhole cover, or otherwise uneven pavement. Gain speed ( > 15mph) and then lightly brake over the rough/uneven surface. You will see the traction control light blink and the regen will kick off. The velocity will continue to decrease. The deceleration (negative magnitude acceleration) will also continue but will change magnitude. The jerk (derivative of acceleration which you can do easily from the graph you get) will show a hump right where the bump happened. This means there was a change in the rate of change of your speed, but the magnitude continued to be negative.

 

The same thing happened to me yesterday while on the freeway taking an interchange. I had cruise control set at 65 mph, disengaging it as I approached the interchange that slows to 35 mph due to the curve. I was coasting when the car suddenly braked, internal warning light flashing, alarm beeping and seat belt locked up. I was alone in the car (thank God) with no cars behind me or in front of me.

I immediately took the car to the dealership only to be told today that they couldn't find anything wrong and that I am more than welcome to take a drive with their technician to see if I can replicate what had occurred. SERIOUSLY?????​

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I can't understand why the Pre-Collission System (PCS) would act as if it were trying to prepare for impact if there was nothing if front of the vehicle. This is a serious safety isse. I could have been rear ended or lost control of the vehicle.​

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If it's a one time only thing, it's possible that an object got temporarily lodged on the front emblem (where the radar is), causing the adaptive cruise control to slow down and further triggering the PCS. Extremely doubtful that PCS would have caused lost of control of the vehicle.