Power brakes went out while stopped with foot on pedal.

I drove 15 min to a post office, powered off the 2004 Prius, dropped my package off, started the prius, and had my foot on the brake for a few minutes while dealing with notifications on my phone.

I felt a strange sensation through my foot on the brake, as the pedal got mushy all of a sudden. I didn't think much about it, started driving away, and noticed the brake felt super mushy and stopping distance was way longer than it should be. I also noticed that the red Brake Light was on, and three yellow warning lights were on: "Warning", "VSC", and one other next to or between those that I can't remember now.

I pulled off the road, powered off the Prius, powered it back on a few seconds later, and nothing had changed: still mushy brakes and same warning lights. I powered off, waited a few minutes, and powered back on. This time everything was normal: the brakes were stiff and powerful, and no warning lights.

I pulled out a bluetooth OBDII scanner from my glove compartment, but couldn't see any codes thrown or in the history. Since I'm not very familiar with the OBD Fusion app, it could have been user error but I spent 5 minutes digging around and I have easily found codes in the past.

Any idea whether I should be worried? This is the first time this has ever happened since I bought the 2004 new.

 

Thanks for the info, all!

No beeps, just lights. IIRC I did feel sort of a vibration in the brake pedal similar to when ABS activates while braking from speed, even though I was stopped, right before it got mushy.

Good idea. I'll bring the car to an auto parts store or dealer who will have a proper code reader.

 

Good points. I'm heading to the Toyota dealer in 15 minutes. They did test my Optima Yellow Top a month or so ago and it was above spec. But one of the posts is cracked from when I dropped it trying to install it, and very fragile. So it is conceivable that could reduce the amps available to the braking system, especially while parked. I will have them test it and I suppose I ought to bite the bullet and replace that battery even though the capacity is fine. It's 7 years old and I have gotten more life out of the Optima Yellow Tops in the past, but potentially losing braking power seems like a very good reason to replace. Autozone seems to have a decent price at $279 delivered to the store.

 

Argh. The Toyota dealer found a code C1357: "Decreasing Pressure Solenoid Malfunction Front Left " in my recent history (but it was not "thrown" which is probably why OBD Fusion didn't present it to me):

C1357 Code Decreasing Pressure Solenoid Malfunction Front Left

They suggested I replace that actuator for $3100 including labor. I was hoping to keep this car at least a few more years, until a new generation of plugin hybrid Prius or other vehicles gets released and supply chain issues ease.

I have a very nice stereo system recently installed which would cost about $3k to transfer to a new car. I have done all the required maintenance since I bought it new. So the car has much more value to me than it would to someone I would sell it to (if I even could). I think I'd be willing to put $3k into this car for a few more years service. It's a lot less than the payments and insurance for a new car.

However, if these actuators are all going to start going bad around the same time, that means four actuators (one for each wheel), and that would probably be reason to let this car go. I'll go read up on this actuator situation. I'll also retest my high voltage battery with the Dr Prius app to see if that's still OK.

For now my thinking is to go ahead and replace the battery with an Optima Yellow top; it's about the same cost as the OEM dealer battery after discounts, about $300 all in. It does seem possible that low voltage could have caused a marginal actuator to have that failure and throw the code, and that higher voltage might keep it reliable for a few more years. I don't hear the hydraulic pump running often as others with failing actuators have reported, but I haven't been listening for it either.

 

Very useful info here.

I have no indication that the dealer read the INF code. Sounds like I need a second and third opinion.

Thank you! I am now pretty sure the dealer service rep didn't fully understand everything he was talking about. He made it sound like the replacement would only fix the one wheel, but all my web research agrees that there is only one actuator assembly for the whole car. This is encouraging, as is the fact that I may not need one at all because it may not be the mechanical leakage issue that seems so common.

Edit: I just emailed the dealer to ask if about the INF code and the Ohmeter tests.

 

I will look into that. But my experience was that Optima batteries lasted nearly twice as long as the other batteries, so even if the Optima only has half the life as in the past that just puts it even. And the Optima is the only one rated as deep discharge (to my knowledge), which is important with the high powered stereo system I have; I always keep the engine on ready when listening, but my system can suck down more watts than the inverter can supply so even then can drain the battery.

 

Okay, big update.... TLDR I'm going to have to replace the actuator and so now looking for best deal on that.
So the dealer who did the test that I reported in post #11 got back to me and said the INF code was 26, and I think mistakenly told me that the actuator and ECU were one unit and both would have to be replaced together so no point in trying to figure out which was at fault. Since I'm pretty sure this is not true, and this was not the first distortion he communicated, I gave up on this dealership and went to another Toyota dealer, where I paid $170 to have them do a detailed diagnostic.

BTW the inept dealership was brand new with a high end hotel like waiting room, while the Penske Toyota dealer below who seemed competent had an old trashy waiting room that felt like a bus terminal.

This time I got to speak with the actual service tech for 15 minutes, answering all my concerns and getting really good info. He said that the "C1357 Decreasing Pressure Solenoid Front Left" which was current but not thrown in my car was associated with DTC (Detailed Code) 28 which I guess is the INF code:

28: Short to +B or voltage leak in SLRFL continues for 0.05 sec or more

He said it is possible that the 26 code the other dealer reported could have been from another freeze frame, although my sense is that it was probably just a telephone-game typo, but for the record I'll note that code works out as:

26: Open circuit in SLRFL continues for 0.05 sec or more when SLRFL is off.

This knowledgeable tech showed me the freeze frame data pulled from the car when the C1357.28 was thrown, which showed voltages on +B1 and +B2 both measuring 14.03V, which I think he correctly interpreted to mean that my battery voltage was not what caused this.

• He said that a defect was discovered in the manufacturing of the actuators at some point, and that the newer ones made after the defect was corrected have a different part number from the potentially defective ones.
• So I definitely want one of the newer ones if I replace mine.
• He said he has seen vastly more actuators than skid ECU's go bad. He didn't say but I inferred that the troubleshooting steps that say to test the ECU first were probably written before the actuator defect was known.
• As far as testing the wiring and skid ECU, he said that it would require $700 of uninstallation to access the ECU terminals. And...
  
• The ECU tests would also only be useful to do while the code was THROWN (and dash light on), but wouldn't serve any purpose if that code and light weren't currently on, which is my situation.
• He said that he suspects the root cause of my actuator failure is the same accumulator issue that most people are seeing and which was covered by the recall. But because
  • my C1357 code is not one that was covered by the recall
  • the recall only applies if the dash light is on and code is thrown (not just current).
  • my 185k mileage is over the 150k limit for the recall
  • IIRC the 18 year age of my car is over the age limit for the recall
• He didn't think my chances of getting Toyota to fix it on their dime were very high, although I could try.
• As far as the safety of driving the car in the current condition, he noted that as long as the dash light is not on, the system is working properly. But if the dash light is on (as it did for me temporarily), then I need to immediately stop driving it. He did note that many people drove their cars into the shop with the light on and just manual brakes, but that is outside my range of comfort.
• This dealership's estimate for replacing the actuator was $1074 labor, $1900 parts, 61 misc which works out to $3197 with tax. I didn't bother haggling with them since I'll probably find an independent shop to

I spent this morning testing my car with Dr. Prius checking the High Voltage Battery.

• Out of five "Full" tests, four showed completely passing results, while the second showed the following under "bottom voltage:" Warning! Suspected problem block 7,8,13,14, [and the rest was cut off of the screen]. I think I'm willing to chalk up that one apparent failure to random fluctuation out of statistical ranges.
• The "Lifetime" (capacity) test results for three tests were: 58.29%, 51.67% (this test was interrupted about halfway through by engine starting), and 54.94% (this test was interrupted about 3/4 of the way through by engine). For reference the results screen says: 90% new, 70% good, 50% fair, 40% poor, lower than 40% need replacement soon. A few years ago my result was about 60% so I think it's reasonable to assume that at this trajectory it is not unreasonable to hope for at least a few more years out of the battery.

So unless there's something I'm missing, I'm going to keep this car and replace the actuator. I ordered a new Optima Yellow Top from O'Reilly for $279 list plus core, shipped to dealer hopefully in one day.

I will start reading old posts about best deals for actuators, but if anyone has advice they want to share here I'd be much obliged. I'm new to NW Austin and if anyone happens to know of a good hybrid shop please let me know.