BRAKE FAILURES ON 04+ PRIUS

Got a specific URL?
.
_H*

 

brake backup power supply kicks in if all else fails.

i smell a rat.

 

I selected "N" while at about 30 mph and made sure that the MFD showed no ICE and no regen, then applied brakes to see if there was any difference in the pedal feel or brake sensitivity over the braking in "D". I think the pedal travelled a wee bit farther before braking, but the braking at that point felt the same, to me.

Can some technician criticize my method, or verify the results?

 

Sounds like another GM 'expert' over at Edmunds. I quit checking over there a while ago as there are lots of kooks and bashers.

I would think that with both the regen units and the regular brakes, the Prius is one of the safest braking systems around.

 

on a side note, i have an early 05 that is in line for the recall. i've noticed lately that my brakes seem to depress too far. when i press the brakes all the way down and release i hear creak type sound. as if something is not lubricated. hopefully it's not too serious and under warranty.

 

I will try that. As I understand it from Prius NCF the back up capacitor battery kicks in and allows the hydraulic brakes to work.

 

If you're in Neutral, there's no regen. Only physical braking,
but it's still controlled by the computer and the rats nest of
solenoids. Yes, braking feel will be different in that case.
.
Braking in N has its uses, too -- for the poster who's noticing
the weird noises or klunks. This topic came up elsewhere around
PC not too long ago, in fact. For a longer piece on braking
oddness and using neutral to fix it, look near the end of
http://techno-fandom.org/~hobbit/cars/prius-log/003.html in which I
went through my own discovery process.
.
Found the earlier PC topic:
http://priuschat.com/index.php?showtopic=11858
.
_H*

 

I hate to be doom and gloom too, but this has been reported to the NHTSA (if you search), so it has to have some basis in reality. And you'll find topics here where people talk about brake 'slippage'. One guy did rear end another car as I recall.

 

Well, I am not certain of the specific complaint but I will share my experience here. I have a 2005 Prius which we purchased in July. Last night on the way home, I stopped off to pick up dinner at a place one block from my house. When I switched into reverse, and backed into the parking spot, the dash warning lights lit up. To my recollection, I had both brake lights (red and yellow), ABS, VSC, and the airbag warning lights turn on. When I saw this, I parked and switched the vehicle off figuring that it might reset itself. After waiting a few minutes, I booted up and tried to move about the parking lot (it was untrafficed in my location). The brakes were HIGHLY unresponsive. In order to stop, I had to really push the pedal down. In response, the nose nearly burried itself in the pavement. I called the Roadside Assistance folks who sent a flatbed and took it to the local dealer.

I called the dealer first thing this morning, but they have not had a chance to determine the nature of the issue. I expect to hear back from them anytime. Is this the sort of complaint this thread was started for, or am I no where close? What was the nature of the initial complaint anyway?

 

Well, to 98% of the people here you're probably a mole from GM sent in to stir up some fear and doubt!

However, I think most instances of the brake failure I've read about are "slippage" where you're braking and suddenly the brakes just aren't applied for a few seconds. Your incident could be related, but who knows. I guess it's up to the dealer to diagnose.

 

Rule # 1

always blame software

h34r:

 

Ahh. Yes, I have experienced that too and just taken it as the "benefit" of switching from regenerative braking to friction braking plus the creep aspect of the transaxle. Never considered it a problem, myself.

I will let you know what the dealer claims the issue is...

 

There's one poster here who had the slippage take his Prius right into the rear of another car.

It seems to be the worst over uneven surfaces, almost like the ABS can't figure out what to do so it just doesn't apply the brakes at all. There seems to be certain stretches of road where it just seems to almost always happen.

 

It sounds like your primary brake system wasn't working. If I remember correctly, the Prius does have a physical brake system (unpowered) that allows you to stop the car in case of a brake system failure. I would imagine that this would be like turning the engine off of a regular car (with power brakes) and trying to stop. With no hydraulic pressure in the booster the pedal feels very hard and ineffective. You have to stomp on the pedal to get any braking force and even then it's pretty weak.

Let us know what the dealer says. I'm curious as this was a question I asked before we bought our Prius - what happens if there's a catasrophic system failure and all your electronics are knocked ou.

--GD

 

I remember reading of this in the manual. It went something like this, "When those lights come on the braking will be erratic, and to park it and call for roadside assistance.".

You did the right thing.

Please, let us know what the dealer tells you. TIA

 

Well, I heard back from the dealer who verified that there was a "code" causing the issue. The technician verified that none of the three possible causes (bad wiring harness, bad ABS ECU, and I cannot recall number three) were the problem, so they test drive it for 15 miles, and returned it to me. :huh:

There was no explanation as to how this "code" was triggered, only the excuse that "we have had cars sometimes do that." :blink:

So what it amounts to is that I went without the vehicle for nearly 24 hours for a spurious issue. Needless to say, this has shaken my confidence a bit:

S.A.: Well, here is your car back (as he hands me the key). We couldn't find anything wrong with it, although the "code" clearly indicated there was a problem. Let us know if it happens again.

Me: You bet that I will!

At this point, I do not even have any paperwork since they returned it to me after the warranty service writer left for the weekend.

I have owned two cars prior to the Prius and maintained one, but this is my first experience with Toyota and their dealers. I hope that they can do better than this...