Recall for brakes DID NOT fix the problem

Greetings,

Before the recall and within a few weeks after I took delivery of my new 2010 III I experienced the sudden loss of brakes with the sensation of a forward surge during a easy braking from about 30 mph. The episode occured after I hit a small pothole with only one front tire, using light pressure on the brake. This happened a few more times over the next few months; all under the same type of condition: braking lightly to moderately and hitting a sharp bump with only on front wheel. The episode lasts about a full second before the brakes automatically reapply and the car slows normally.

In fact, I found a street that had the right conditions and I could duplicate this brake problem every time. I told my dealer I could recreate the problem and asked if they wanted to ride with me to see it and feel it themselves, but they declined for whatever reason.

I had the recall procedure done recently and the ECU was flashed according to the workorder. However the exact problem remains; I can still cause this braking anomoly to occur. I am especially concerned today because this was the first time I had it happen where I came very close to not stopping in time to avoid hitting the car in front of me.

** I can clearly see how someone can have this happen and because of it have a small collision under the right conditions **

Has anyone else been able to create (recreate) this braking problem?

I am somewhat technically inclined, but I will defer to those more familiar, but my guess has always been that the ABS or Traction Control system is temporarally confused by the front wheel signaling a slip or rotation speed change. This seems to cause almost like a "reset" of the system and for that second or so, you have basically no control of the brakes.

I was able to recreate it on one particular spot and still can even after the brake fix. The difference is that now the brake "pause" is significantly shorter than it was before the fix. It has been discussed here on PC in multiple threads and probably thousands of message.

BTW, welcome to Prius Chat!

From everything I have read .... the situation you describe is a characteristic of all hybrid vehicles and occurs between regen and braking. I have felt the sensation, and it does cause a moment of uncertainty .... in my instance, I do not think the car actually "surged," rather the de-acceleration was momentarily stopped, and it felt like a surge. Again, in my situation, there is a sunken [small] utility line cover down the street exactly where I am coasting [regen] and start to apply the brakes for a stop sign. A little more brake pressure,the brakes activate, and the stop is normal and under control. Naturally, I try to avoid the spot which I can do easily.

I too had the ECU flashed .... but it was more a precautionary measure ... I was fearful that if I should have an accident, the insurance company would cite my failure to have the work done as a cause to decline payment.

If the fix didn't change the length of the pause, maybe it didn't happen. Maybe the tech went on break or to lunch and yours' didn't get done. Take it back to the dealer and/or contact TMC directly.

As I have noted, every vehicle with ABS has something of this problem. The issue is how long the pause lasts. I don't think it can be eliminated, just shortened.

And for goodness sake, keep braking through the pause- it will stop!

I will respectfully disagree with the above statement. While every vehicle with ABS may have some "problem", I have never felt this type of sensation before owning this car. I have felt ABS shutter in the break pedal on many other cars, but this is very different. If this is a hybrid characteristic, that I cannot argue since this is my first hybrid. However, this "problem" is certainly severe enough, long enough and pronounced enough to cause concern.

I don't think they (TMC) have solved the problem yet, even with the recent ECU reflash. I'll bet we hear more about this from TMC.

It's a normal ABS issue, but the effect is exacerbated by the transition from regenerative to friction braking. With regenerative braking, you have only the front wheels braking, and they are connected through a differential. This means that a loss of traction with either front tire will force the Prius out of regeneration and into friction braking.

The net result is that you feel it more often than you would with a normal car, and the result is more pronounced.

Tom

Keep looking, there are a lot of posts here about the commonality of ABS issues when the system thinks slippage is occurring. My Cadillac would do it crossing railroad tracks or on really rough pavement. My Blazer certainly does it when I'm on a rough, dirt 4WD road and need to brake.

And I think I told him to worry about it, and to make sure it was fixed. I do want the OP to make sure he doesn't get too freaked out- if you know it's there and just keep braking, you can survive til you get it fixed.

A second really feels to me like it's too long. I have not had any regen->ABS issues but I've only braked lightly so far and hardly driven it. However, IMO a one second delay is just not acceptable. If this is happening predictably post-ECU I'd call Toyota--not your stealership--and get them on the phone. They cannot afford this kind of news to be going around.

There has been at least one other report of the SSC-A0B not being performed. Take it to another dealer and ask them to check.

Bob Wilson

Same here. I drive with one wheel over the pothole and it slips. I had a thread about this issue. Whether this is safe or normal is up to you to decide. I'm not too hung up about it bc it only seems to happen to me in fairly deep potholes. Also it is not common for me it seems to happen only in one segment of the road i drive everyday. At any rate I'm just conscious driving over potholes and braking over them in general.

Is it that difficult to apply more brake as soon as you feel the car slipping?

I had mine fixed at the dealer 'flash the abs computer' but it happened to me once after the fix. I don't think Toyota has a clue what they are doing.

I really don't think there's a problem--more a quirk of the braking system. My brakes work well. There is a tendency for the VSC system to activate briefly (light flashes on dash briefly) over rough spots if your tire pressures are high--around 40 psi.

I got mine reflashed yesterday morning and so far so good. I have one road I drive on everyday that when I come up on this one stop sign the road is rough. Before yesterday I'd say 50% of the time I had the brake fade coming up on that stop sign. Well I have been on that road four times coming up on that stop sign and not once has the brake fade situation occurred since having it fixed.

Knock on wood as they say. Two days isn't really a test but if it continues to work I'm not going to complain.

DVA if you feel that unsure of the car you should probably not be driving a Prius. There is nothing wrong with the car. Have the dealer re-check the programing of the braking system and reflash it if necessary. The system has three braking systems, the ABS system, the regenerative system and the service brake, commonly know as the friction brakes, all controlled by a computer. The computer takes a nano-second to figure out what you are doing, keep applying pressure to the brake pedal the car will stop normally unless you are traveling at too high rate of speed. If you let off the brake pedal and reapply presure to the brake pedal the computer gets confused as to your intentions. Just keep braking instead of complaining.

I'm not sure what version of the ECU flash that I have on my car. Can someone tell me if the recall ECU flash is required by Toyota? Are some dealers doing the recall ECU flash even if the owner does not want it? Is the dealer the only one who can tell which ECU flash version is in my GenIII Prius? Are dealers charging customers who just want to find out the flash version without making any updates? The service salesperson is pushing for me to do the flash "upgrade" even though I am happy with the car as it is and have no problems.
4/5/10, I had a typo earlier. I have a Gen III Prius. Sorry for the confusion.

DITTO

:rockon:

It is a safety recall. The defect does not happen frequently. It is a liability issue for both you and Toyota if you do not get the recall. It is hard for me to believe that anyone that has experienced it would not want the updated software. Since there is no charge for the upgrade, I'm not sure why you would want longer abs braking distance in your car. Is it because you are worried about other problems with the update?

There are some that are still experiencing problems. I see bob wilson is offering accelerometers to see if there are still problems after the fix. I have not had any problems after the software was updated. I'm sure that the software fixes some problems, but with the continued problems with some drivers I wonder if there are some cases toyota has not fixed yet. Or if in these cases the dealer did not update the software.

My FJ Cruiser will also do that. Indeed, the issue is frequently and very openly - sometimes hotly - debated over at the FJ forum

Looks like some Toyota's have this issue a lot more than others

The reflash is only for the Gen III Prius.

Tom