C1256 After replacing brake actuator… twice now!

Hello everyone,

I’m about at my wits end trying to solve a brake actuator issue.

Here’s where I’m at:

Had ABS, VSC, and ((!)) lights come on with a Low pressure of Accumulator flash code

Here is a list of the flash codes when I started into this mess:

(ABS: 31, 42
*31 explanation: Front Speed Sensor RH Circuit
(Resolved when I found rodent damage on the upper speed sensor wire and fixed the damaged wire - thought it worth mentioning if it helps anyone’s brainstorming process to know there was confirmed mouse damage)

VSC: 43, 45

((!)): 36, 57
*57 explanation: Accumulator Low Pressure)

… So after taking it to a local shop and paying for a diagnostic, they confirmed that the brake actuator needed to be replaced (a VERY expensive job.).

I decided to order a used actuator on eBay for $350, watch some videos, and install myself, as I couldn’t justify spending that much. (Just had a new HV battery installed - still recovering from that expense!)

I was able to install the used actuator I purchased and everything seemed to go smooth enough.. only now when I stepped on the brake pedal, there was a constant beeping - an alarm to let me know there was an issue in the brake system.

I had read that the brakes need to be bled using a special scan tool after replacing the actuator, so I decided to take it in to the dealer to have them do the brake bleed.

They refused to bleed the brakes, saying that I had a code pointing to a bad actuator and it needed to be replaced.

Fair enough I guess.. I realized that buying a used one was a bit of a gamble.

Still, I thought there might be a chance that the reason I was getting a code after installing the replacement actuator was due to the fact that it never got bled properly.

So I bought the XTool d8 scantool which has ABS bleeding feature and decided to give that a go myself, as the dealer wasn't willing to do it.

the code was c1256: Low Pressure of accumulator (and intermittently also C1252: Motor of Hydro booster pump)

I kept having issues with the bleed process where the scantool would give me error messages. (Finally discovered this was due to a weak 12v battery. Replaced that and was able to make it through the bleeding process…)

No luck on the code or the beeping going away.

At this point I figure it must have been a bad actuator that I installed.

So the eBay seller honors their warranty sends me a replacement actuator.

Just finished installing that, ran through the bleed process, and am STILL having the beeping and the C1256 (low accumulator pressure code) and C1252 (motor of hydro booster pump)

I’m starting to think that maybe the issue never was the actuator, and that something else is causing that low accumulator pressure code?

what are the chances that my original actuator, the replacement actuator, and the second replacement actuator all have the exact same issue?

Lastly, I’ll mention that the new 12v battery I had just installed died a few days later - was reading 5.9V and my battery charger couldn’t revive it… so I’m assuming the booster pump motor is running continually and draining the 12v battery?


Any help and direction at this point greatly appreciated

 

Also thought it worth mentioning:

On both of the used actuators I’ve put in now - immediately after completing install but before and during bleeding brakes, I have heard them running.. and then after a little while, they start to make more of a choked / gurgling sound.. then I stop hearing them at all. I assumed air was getting into them? But after multiple attempts doing the ABS bleed with my scan tool, I still don’t hear them working.

So I’m led to believe that they are functional when I install them, and then something is happening shortly after?
Also, am wondering if that C1252 (motor of hydro booster pump running longer than usual) code means that the pump motor is working so it is safe to assume that its not an electrical issue leading to the pump? Also the fact that I initially hear the actuator working makes me think that the issue isn’t electrical?

 

Oh, and one more thing that may be relevant: During the brake bleeding process (first it has me bleed the Front Left and Front Right with the ABS relays removed, then it has me press the brake pedal 30 times in 30 seconds while it activates certain things, then wait 2 minutes, then reinstall relays and bleed the rears, and lastly has me open the Front left one more time as it activates something) no fluid is coming out when I open either of the bleeder valves for the rear brakes.. but the valves themselves aren’t clogged because if I squeeze the line a little by pinching it in my fingers, then a small amount of fluid does come out.

 

Thanks for your reply -

I’ve been bleeding the brakes solo, but I do use a clamp to keep the pedal depressed while I crack the bleeder open, so it’s helpful to know that I should be getting something coming out the rears. And just for clarity, mine is an ‘06, so it is Gen2 same as yours.

And what I’ve been replacing is the brake actuator assembly. I’ve inserted a link to the picture. Only mine didn’t come with that separate part on the bottom in the picture with the wiring harness (looks like that might be the modulator valve?)

There is a separate pump that mounts right next to the actuator assembly that you have to work around when installing the actuator - not sure if that’s the Accumulator?

Added another photo showing both - the yellow arrow is the actuator assembly I’ve been replacing. The blue arrow points to the other pump in question, which has been moved up and out of the way.

 

On further research, it looks like the accumulator is a part of the actuator assembly (the black cylinder in the picture), so that would have gotten replaced each time I changed the actuator assembly as well.

 

Thank you for the perspective. It seemed almost impossibly unlucky to me to have 2 defects in a row… but if there’s no other cause of that code I guess I’d have to accept that as true.

I do know that it’s a common issue with 2nd gen prius… and maybe the reason the car ended up getting parted out in a wrecking lot is because the people were driving around with a malfunctioning brake system!

We’ll see how far the seller is willing to honor his “warranty”… though I shudder at the thought of doing the job yet again at this point!

I’m also wondering if air in the actuator would cause that code..

From what I’ve read, it seems the ABS bleed process with Techstream is more extensive than the one the scantool I bought walks me through… really wishing the dealer would have agreed to bleed the brakes, if for no other reason then helping me trouble shoot this.

 

Any ideas on why no fluid would be coming through when I go to bleed the rears? Again, I know the bleeders aren’t clogged as a little fluid comes through when I squeeze the line..

Not sure exactly what role the relays play in the brake system, but would a faulty relay cause that to happen?

 

To anyone following this and/or helping brainstorm:

Just learned from another thread that when the brake system goes into fail safe mode (hence the buzzing alarm and the loss of power brakes), you won’t get any pressure coming out of the rear bleeders.

So, that might be the explanation for why I’m not getting fluid out of the rears.

Going to try disconnecting and reconnecting the brake lines connected to the actuator again, on the chance that they didn’t make a proper seal and that’s why it’s not able to pressurize.

Also going to see if I can find any other wires that have rodent damage - on the chance that the “low pressure” code is coming from a damaged wire that gets input from the actuator’s pressure sensor

 

Well, ostensibly it’s now fixed.

I bit the bullet and bought a new actuator from Toyota. Paid something like $1200 for it.

Pretty sure that was the ticket.

But a few things I did different on install:
1) the new actuator came with a new resister, so I installed that (it mounts from inside the car, sort of behind and above the e brake pedal - look for a blue connector and a two silver braided wire protectors… you can see the part pictured in the stock photo above)

2) I did a thorough manual bleed of all 4 brakes BEFORE reconnecting my 12v battery and hybrid battery (bled both fronts something like 6 times.. and the rears a few times as well.. just when I thought I’d had it all, I would get a little more air coming out. At first the pedal was going all the way to the ground and I didn’t think I was going to get anywhere, but eventually air came out and it stiffened up.

Thinking that may have helped lessen the amount of air that got into the actuator. When I completed the Abs Bleed procedure with my scan tool, this time fluid came out the rears.

I did have to do the scan tool bleed procedure twice, as after the first time the buzzer and the low pressure code came back. Upon the next round, a little more air came out of one of the bleeders.. so I’m thinking those actuators can be really finicky when air gets in them.

made a video of the whole process - will post a link here once I get it posted somewhere.

thanks for the help and the ideas everyone who chimed in

 

For any who may find it helpful, I’ve made a video of the entire process of the actuator replacement as well as the scan tool assisted ABS bleed

here it is:

https://youtu.be/px9CHQxNnac?si=8nE7KRNZATSqctv9