Last post on Sep 03, 2013 at 5:22 PM
You are in the Toyota Prius
What is this discussion about?
Toyota Prius, Brakes, Hatchback, Sedan
Go to NHTSA to file a safety complaint.
Or call Monday-Friday (8 am to 8 pm ET) (888) 327-4236 TTY: (800)424-9153
#166 of 370 Re: 2009 Brake problem [phaters]
Feb 09, 2010 (12:29 pm)
Please see my previous post #81
I took my Prius in and had them look at it on Dec 15th a couple of weeks after I had the accident. They said that everything checked out fine and that it was probably my anti lock brakes kicking in(I moved to Seatlle from Minnesota and I know what anti locke brakes feel like, that wasn't the problem). Since then going down the same hill the car has accelerated when going over a pothole in the road. I called Toyota back and they said that my car is not part of the recall and that when they looked at my car in December they checked the brakes and the accelerator and all checked out! I feel like there is not much else to do. I called them again today and left a message that I want them to take another look. My insurance company said to just keep bugging them. After reading the other posts, the service guys at Toyota must have been told to tell people that they have never heard of this problem! I also feel Toyota should fix the bumper that was dented from the brakes failing to work! URG
#169 of 370 Re: 2009 Brake problem [phaters]
Feb 10, 2010 (7:18 am)
Have you filed a report with the NTSA? They have an online form. I personally believe you as someone who's had the same problem.I think unless people start to complain to the right people, this will be swept under the rug. I encountered the problem one time in my 2007 Prius in December during an ice storm. I live in minnesota and am all to familiar with the feeling of Anti-lock brakes on ice. This was a completely different experience. I had it happen a second time yesterday. I hope it never happens in a busy intersection.
#170 of 370 Re: 2009 Brake problem [phaters]
Feb 10, 2010 (10:11 am)
Hybrid vehicles, unlike ABS implementations in non-hybrid vehicles, have two modes. Mode 1 simply disables regen braking and brings frictional braking online if it is not already. This transition, when frictional braking was not already online, is the cause of the "lurch" or "surge" seat of the pants "sensor" feeling, in reality a brief "lessening" of braking HP.
Once frictional braking comes fully online and if impending wheel lockup detection persists then ABS goes into mode 2 and you get that standard vibratory brake pedal feedback "signal".
In the case of a short bump, pertubation, in the roadbed that causes a brief separation of a driven wheel with the roadbed it is highly likely there will be no cause for ABS to enter mode 2.
#171 of 370 Re: 2010 Prius Owner with Brake issue [tryingedmunds2]
Feb 10, 2010 (1:05 pm)
"...ABS is capable of PWM, Pulse Width Modulation down to 10's of milliseconds is good.."
While electrically/electronically the solenoid voltage can be switched on and off at those rates the mechanical time constants involved only allow a "switch" rate on the order of 100's of milliseconds.
The PWM dutycycle is controlled by the ABS ECU in real-time, and it has two "masters". First, it will not allow the front wheels to slow very much more rapidly than the rear wheels, and vice versa. Second, if it detects that ANY wheel is too rapidly approaching lockup it will instantly release brake fluid pressure on that wheel and will not re-apply pressure until the wheel rotation rate has again risen to some "target" as defined by the current roadspeed.
#172 of 370 2005 Prius Sudden brake problem too
Feb 13, 2010 (9:34 am)
Might as well add my two cents worth here. My 2005 Prius (bought new) acts as if I have slammed on the brakes with only a very light touch on occasion. Mostly mornings. This since the very first year I had it. Toyota of Tampa Bay says they know nothing unless they see the problem. Even just an amateur search on the web shows this is fairly common problem. I filled out the little complaint form at the DOT site of "Office of Defects " and I received back a notice saying if I wanted to file a complain .......call this number.That after already filling out a complaint form. LOL. I notified Toyota but they have yet to give me any indication that this is something they are interested in fixing. It's OK though I have kept records and so if we get in a wreck at least my kids can sue everyone involved and maybe get a few bucks out of the criminals.
#173 of 370 Re: 2005 Prius Sudden brake problem too [phydo]
Feb 13, 2010 (2:46 pm)
Do the brakes WORK; i.e, do they stop the car?
#174 of 370 A0B appears to fix problem
Feb 14, 2010 (7:35 am)
I'm still testing but preliminary data indicates A0B fixed the brake pause. I used the following pothole for pre-patch testing:
The pothole, near side, was used for testing: ~4-5 inches deep and 7 feet long. I approached the pothole at ~20 mph since 19 mph is a documented threshold for braking transition. Before the patch, the regenerative indicator showed ~75% but after the pothole it dropped to ~20-15% and there was about a 50% reduction in braking force:
After the patch, the same test scenario showed ~50% regeneration and no reduction in regeneration after the pothole. Accelerometer testing showed no reduction in braking force:
It took a while to realize that the brake pause was not the same as our rain-slick Huntsville streets. I have one more test to run but it will take drizzle wet streets. But based upon the pothole tests run on Saturday, Feb. 13, the patch A0B works.
#175 of 370 Re: 2007 Prius [avucarguy]
Feb 14, 2010 (8:29 am)
I have a 2007 and a 2010. The 2007 has always had this type of issue. Living in NJ I also notice it on snow and ice bumps..especially with the recent snow accumulation.
The 2010 has not engaged the VSC or AB as much as the 2007...but it has happened.
I honestly take this as normal...a Prius may start with a P but it ain't a Porsche.