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How To Deal With A Toyota Prius C1256 Failed Brake Accumulator Trouble Code

If you are a Prius owner who has dealt with a C1256 on your car, you know how much it costs to fix it. If you want to avoid the issue tune in.

Hey, fellow Prius owners! It is good to see you back. As many of you know, I write about the Toyota Prius. I love to cover how great the car is and what you can do when failure happens. As good as Prius is, the vehicle is not without flaws.

In this article today, I want to talk about a costly repair we all know as the brake actuator. I want to cover what this problem is, what you can do about it if you encounter it, and how to avoid it. First, we will look at what the code is, then why you get a failure and wrap it up with what you can do to avoid it.

C1256 Low-Pressure Accumulator Trouble Code
The trouble code for your Prius sets when the pressure inside the brake unit can no longer be maintained. The trouble code C1256 is set, and there is a long buzzer from your car warning you that brake failure has happened.

2010 Toyota Prius Brake Reservoir

The other thing that happens with this is that your Prius can no longer go into regen braking. That means if you continue to drive, you will likely over-discharge your hybrid battery.

Your best bet here is if you have a hybrid battery code and a brake code, take care of the brake accumulator first.

Why The Brake Trouble Code Happens
Gen 2 Prius is relatively bulletproof. It does have weak spots, though. Some shops even call these repairs "the big three" and the brake accumulator is one of them.

Toyota Prius C1256 low pressure failure

What happens in our Prius is that over time, tiny leaks in the accumulator cause pressure in the tank to drop. This action results in the motor having to run more often to maintain system pressure.

If you hear your brake accumulator running about every 15 seconds or so, you are close to failure. Listen intently as you get in and out of your Prius for the noise. Your brakes are very important if you have not noticed.

What You Can Do To Avoid The Issue Or What To Do If It Happens To You
I do not think that there is ever any mechanical device on our Prius that won't ever fail at some point. Everything has a shelf life.

Shelf life does have parameters, though. For instance, someone who does the routine maintenance on their car would know that changing brake fluid will significantly enhance the lifetime of your system. Removing old worn, water-filled fluid and replace it with suitable clean fluid, will have a massive impact on how long your brake actuator lasts.

There is no guarantee of how long it will last. I would hope that no, you never need to replace it. In case you do, here are some suggestions to help you stomach the cost.

First, only install new. The reason for avoiding used parts is many of the used units probably are either faulty or will fail soon after. If you just paid to have a new-to-you unit installed and then it fails, sorry. You will have to pay the labor again to do the same process. Buying new will get you into a unit that will work properly.

Second, shop around. While you Toyota dealer is charging $2000 to $3500 for replacement, a local hybrid specialty shop could be a better bet. I have seen prices right around $1850, which is high, but still less than the dealer.

Third, if you plan on doing this DIY, make sure you have the proper equipment to do the procedure the right way.

It sucks to have a failed braking system on your Prius, but remember if you take care of it, then it will take care of you. If you need help or have questions on your Prius, feel free to reach out to me on Twitter or Facebook.

That is all for today. I look forward to seeing you in the next story. Now Is The Time To Get Your Hands On This LImited Edition Toyota Prius

Watch this Toyota Prius truck with a nice little bed and click to subscribe to Torque News Youtube for daily automotive news analysis.

Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter is also an Instructor of Automotive Technology at Columbia Basin College. Peter can be reached on Linkedin and you can tweet him at The_hybrid_guy on Twitter. Find his page on Facebook at Certified Auto Consulting. Read more of Peter's stories at Toyota news coverage on Torque News. Search Toyota Prius Torque News for more in depth Prius coverage from our reporters.


David W (not verified)    May 11, 2020 - 4:35PM

The brake accumulator is a touchy thing. There was a letter about it saying if we got error lights it would be replaced on warranty up to a certain date. We never had error lights but a few months after that certain date a brake fluid change was being done by the dealership and they phoned to say that the drain plug had sheared off its threads when they took it out so they were going to do a repair to the drain plug. A while later they called to say that the drain plug was fixed but the accumulator would not draw in the new fluid to build pressure, so I guess the fabled failure occurred while it they were draining it maybe? Anyway the shop were very good and agreed to replace it at their own expense, including supplying us with a rental for the few days that took while parts arrived. I think we paid maybe a few hundred for the new parts but the labour bill was in the thousands so I feel like we got off easy. Still do think its weird that it failed while it was in their shop but if their objective was to sell me a $200 part that it cost them $2000 in labour to put in that would be an odd business model.

yes i got the C1256 (not verified)    February 4, 2021 - 9:51AM

it went rather randomly .. sort of .. that 'pumping noise' which kinda sounds like the hot water cold start pump forthe thermos .. was always a ' is that the thermos pump' never knowing it was a brake pump .. had been hearing it run more often but never thought it meant anything ... yeah that's how its getting close to failing running more and more to keep up pressure until pressure falls below critical .. for me this was about 165000 on the odometer ...on the 2005 prius

Penney Robinson (not verified)    January 22, 2022 - 12:17PM

A friend of mine is selling his 2008 Prius. He has told me that the brake actuator light has come on, but only once, and that was quite a while ago. I am thinking of buying this car. Should I take the risk?

Elizabeth Benjamin (not verified)    June 27, 2022 - 5:16PM

I have a 2004 Prius, bought new and religiously maintained. About two months ago the brake light and yellow caution dash warning came on, but I could not feel anything different in the brake function. I replaced the hybrid battery at 132000 miles, and now have 199200. The A/C quit two years ago and was told it would cost around $2600 to repair (mostly time and labor as the whole dash would have to be removed to get to the leaking part).I passed on having this repair as I am 82 and living only on Soc. Sec. and can't afford it, so when I was informed by the dealer (all servicing has been done there) that it would cost around $2600 to fix this new problem I am at a blockade since I can't afford that either. Thinking of trying to sell it since the rest of the car has been well maintained, and with the high price of gas and new cars someone would be getting a good vehicle for the cost of those two repairs. I am open to hearing any and all suggestions.

norman smith (not verified)    August 30, 2022 - 10:08PM

We ordered a 2005 prius back in September of 2004 with all the extras. We now have more than 200k miles on this vehicle. Normaly we run around in the prius, but it sat in the garage for about two weeks this month. On August 17 I decided to take the prius out for for a drive. When I started it up there were multiple displays on the dash, and just briefly the symbol flashed for the battery and went back off, and then came back on, but went off. I pull the vehicle back in the garage and call my toyota folk gor an appointment. Before I got out of the drive way the battery symbol appeared again and stayed on all the way to the dealership. They ran a dignostics and codes C1256 was stored (low accumulator press.) Code P0A80 was stored (replace hybird batt. pack). Our prius has 201,565 miles and its been a great car. My question has to do with the brake actuator. If the battery if over-discharged due to the loss of regen braking, will the replacement of the brake actuator assy correct the battery?