Brake failure 2005 Prius

Back in April 2007 in this thread I wrote:

datapoint: I haven't had a similar problem ever since. I can sometimes tell that the brake ABS is kicking in briefly after going over bumps but I never seem to lose the ability to brake at all. I'm looking forward to buying a 2010 model just a bit cheaper because of all the bad press.

 

The cavalry may be on their way: Early Priuses may have braking issues - Autos- msnbc.com

 

I was a happy 2004 Prius owner until 4 days ago when, while driving at about 60 mph on a foggy/drizzly 60 degree F. day on freeway blacktop, all warning lights on the dashboard suddenly illuminated, after which I took my foot off the accelerator, began merging across lanes to exit and detected significantly reduced braking power. It is a miracle that I live to tell the tale. I kept my cool and was able to exit the interstate and slowly stop the car by depressing the brake pedal full force. Only the passenger rear brake was even partly operational. . Towed vehicle to Toyota dealership where, after 3 days of electronic diagnostics and conversations with the regional service advisers, it was determined that the computer governing the ABS needed replacement. This will be a costly repair but more importantly my sense of safety has been eroded. Has anyone else had this frightening experience? (FYI: odometer110K miles, bought new, gently driven, impeccably maintained)

 

^^^
Never had such a problem. Did the dealer have any DTCes (diagnostic trouble codes)? If so, what were they? That would help us a lot in determining whether their diagnosis is correct.

Since it sounds like you feel this is a safety issue, please file a safety complaint w/NHTSA at Home | Safercar -- National Highway Traffic Safety Administration (NHTSA).

 

Thanks for your comments. DTC's were unrecoverable for electrical reasons that exceed my understanding. I just e-mailed a safety complaint to the NHTSA.

 

Please read http://priuschat.com/forums/gen-ii-prius-main-forum/88444-2005-prius-woes.html for a cautionary tale on paying for an expensive and completely unnecessary brake ECU replacement. Have you have the inverter cooling pump replaced? Is it in proper working order?

 

Since seilerts is mentioning the inverter cooling pump, you might be interested in http://priuschat.com/forums/gen-ii-...ump-dealer-letter-technical-instructions.html if you haven't received the notification, for some reason.

 

Replaced inverter pump 4 months/4,000 miles ago, but thanks for the thought.

 

How about your 12V battery? Original? Replaced? Tested? And you are confident that your IC pump was replaced correctly and was in proper working order at the time? IMHO, having a brake ECU itself fail is 1/1,000,000.

Try this on for a scenario. Your dealer replaced the IC pump but didn't bleed the cooling loop correctly, or left a hose clamped shut, or introduced a slow leak. The car finally recognizes that something isn't right and sets code P0A93. This shuts down the DC converter. An alternative is that the DC converter itself has failed. Regardless, all of the cars electronics run of the 12V battery. If your 12V is older than a year or two, it runs down quickly; if original, it perhaps lasts only seconds before the bus voltage falls below what is required to run the computers and power the brakes. The brakes set low voltage codes before the brake ECU shuts down. The low voltage shutdown of all ECUs erases all codes except for the brake codes, and leaves you with perhaps one or two pumps on the brake pedal.

Because the only thing that comes up on the scanner are brake codes, and because the service manual specifies ECU replacement if a problem is intermittent, you wind up spending thousands to replace the part that is not at fault.

If anything, screw the dealer and get your car to Luscious Garage in SF or Art's Automotive in Berkeley for a second opinion. They will definitely fix it for far cheaper, even if it is the ECU.

 

If the 12 volt is the original, it's almost 100% certain that it needs to be replaced. To test it, see http://priuschat.com/forums/newbie-...g-mpgs-dropping-test-battery.html#post1020264, but I would let the car 8+ hours or overnight before checking it. But, I'd imagine the Doctor's car is at a dealer now.

Patrick Wong (aka 1 of our repair experts) and others have noted that for some odd reason, getting the 12 volt "tested" by the dealer seems useless. Here's one of his most recent posts on this http://priuschat.com/forums/gen-ii-...after-being-turned-off-then-wont-start-3.html.

I'm not saying this is the cause, I'm just pointing out something that will need replacement now if it hasn't been changed.

 

A disclaimer: I am not mechanically inclined, so I am at the mercy of those who repair my vehicle. I have no way of knowing if the IC pump was replaced correctly. The 12 volt battery was replaced 4 months ago. My Prius has always been serviced at my local dealership. The brake failure occurred near Richmond, CA and my car was towed to the Toyota dealer there, which is 60 miles from where I live. Towing the vehicle to the more distant "second opinion" garages that you mentioned would be quite costly in that they are 15-30 miles away from where my disabled Prius is currently housed. Just to be clear, the car cannot be driven as it is. After testing, reprogramming and taking the vehicle for a test drive, the service technician rolled through a red light and half way into an intersection when the brakes once again abruptly failed.

The scenario that you describe is indeed plausible. As a physician, I follow the logic, although the idea that the computers and braking systems are so dependent on a 12 volt battery troubles me. I also have difficulty accepting what you state as a "1/1,000,000" chance of an ECU failure. Other computer systems "crash" regularly, and the failure odds that you cite exceed the safety standards for cardiac pacemakers! Just curious, is your opinion regarding ECU reliability backed up by objective data?

 

Come on, Richmond to Berkeley is a stone's throw! Call Art's, describe what you have posted here, and see what they can do for you.

Okay, so maybe 1/1,000,000 is a stretch, but the point I was trying to make is that almost every time a faulty ECU is diagnosed, replacement is not necessary. I have helped with two such vehicles since Christmas, my Mom's 03 Highlander, and a friend's 07 Prius, with "replace ECU" written on a dealership invoice, and in neither case was the ECU faulty. Often times, a dealership tech doesn't know Wth the problem is, so they give you a ridiculous quote, to cover the time that it will take them to actually figure out the problem. And you don't need to spend thousands on a new ECU, if that is indeed the problem when a used/salvage will do for less than $100 + programming. Your case is an interesting one, since it sounds very much like a power failure/accumulator problem. Just trying to help, seriously. I personally would take a very close look at the last services that were performed on your car, namely the 12V battery replacement, and the IC pump replacement, since both of these components are almost always involved in the weird stuff happening cases.

 

Sounds like someone wants to complain more than they want actual help. This is evident by the multiple posts copied and pasted everywhere.

 

Thank-you Seilert.for your advice. I will call Arts in the morning, although the $12/mile towing costs would likely eliminate any cost savings as compared with dealer service rates.. I regret if my desperation was off putting to my Sacramento neighbor F8L. I am out of my depth on mechanical issues, and feel as helpless as many of you would feel in a hospital ICU. Loosing braking power on I-80 was such a terrifying experience that I find it hard to remain objective....

 

It's not you Barbara. It's that we often have people come into the forum proclaiming some sort of disaster then they refuse to accept help and followup research. They fail to produce error codes or anything else and then they disappear. Those kinds of posts smell suspiciously of hyperbole and smear campaigns.

I truly hope this is a simple and inexpensive fix for you like Sielert has posted. Regardless, I feel for your position. That is indeed a scary experience. I apologize for my earlier post.

 

Installed price of a new computer is at least $2,000, whereas a used one is maybe $75 + labor.

My primary thought here is that it is not the computer, and the dealer will come back and say, "the computer also fried the accumulator and that is another $2,000 please."

EDIT: I also wonder if it is simply the brake pedal stroke sensor. An intermittent failure with that would also lead to "replace ECU" in the troubleshooting chart...

 

Certainly a hair-raising experience! Before any major repair it's a good idea to get a 2nd opinion. If another problem manifests and the same dealer recommends another expensive repair, take it to another dealer.

 

It's only 15 miles from Art's Automotive -- the hybrid version of the Mayo Clinic!

 

Agreed w/the above completely. I have observed exactly what F8L's described many times. When that happens, it ends up being a total of waste of a lot of people's time.

 

I'm having a brake issue, but it's different from what the original poster described. Sometimes the brakes seem to skip and hesitate for a brief moment. I've noticed this issue most consistently when I'm going down one of several small neighborhood hills shortly after starting my car. I'll tap on the brake pedal, but I don't feel the brakes take hold as I expect. My 2005 Prius has 98k miles. I've maintained it carefully. Recently (at 96k miles) the dealer replaced all four tires and the front brake pads, and resurface the rotors. I only began to notice this issue very recently, after the work at the dealer.
Why this brake issue? Is it the uneven transition from regenerative to friction braking? Is it likely to get worse? Is it a safety issue? What would you do?