Brake Accumulator failure C1391

I will share a tidbit with you guys. If you go to an oem parts seller they will show your number as well as an updated number. I would guess that the updated number would probably swap out without programming. I didn't go that way because I like the easy route. A handful of these have failed, and they are crazy expensive new and dirt cheap used. If mine fails again I may look to find another number, but I would bet it doesn't fail before the other issues of a gen 3 begin to show.

 

It's funny you say that I think flushing the brakes is actually easy if you have the right tools. I borrowed a friend's SnapOn tablet and it runs through all the automated steps one by one in a Wizard type mode and I flushed all the brake fluid in about 45 mins in hopes that would fix the problem. I'm pretty lazy and didn't really want to research what is involved in swapping the actuator. I'm probably just going to drop it at a friend's shop and pay the 2-300 bucks.

Did you have a write up on how to swap the actuator or did you just figure it out yourself?

 

Thanks for the link, I think that's the first time I've seen a picture of the actuator. That is the part that you replaced that is UNDER the accumulator right?

 

Actuator mounts on the firewall, not under the accumulator. See the pushable rod sticking out from the actuator? That sticks through the firewall. Brake pedal pushes it.

-Chap

 

I definitely did NOT figure it out by myself. I would not have attempted the swap without extensive help from member @borgestes via PM.

Here is my attempt at a summary of our long conversation:

Abbreviated steps:

1. Find the part number of your faulty brake actuator
2. Purchase replacement accumulator
3. Remove the faulty actuator
4. Install the replacement actuator
5. Flush the brake system

Tools needed: metric socket set and flare nut wrench set.

Extended steps:

1. I give advice on how to find the PN of your actuator without any disassembly here:
Brake Accumulator failure C1391 | Page 2 | PriusChat

2. Purchase a replacement accumulator from a salvage vehicle (check eBay) with the same part number as the one you are removing. Purchasing a replacement actuator with the same PN will allow you to avoid reprogramming a different model number. However, there *may* be an advantage of purchasing a newer PN and reprogramming, although we don't have any confirmation on whether newer PNs have an improved design. Note: most eBay sellers do not list the item by the part number, but rather a description, i.e., "2011 Prius brake actuator." However, these sellers very frequently misuse part names because the naming system is so confusing (as detailed extensively in this thread). So sometimes a part is called an "actuator" when it is the "acumulator" or something else. Making matters worse, many salvage sellers do not include a photo of the actual item, making it impossible to determine if they are selling the correct part for you or not. My advice: ask the seller for an actual photo, including a photo of the part number. I paid $110 for my correct part from a salvage car with 45K miles.

3. To remove the faulty actuator:
a) DISCONNECT THE 12V BATTERY. This is important so that you do not throw new codes when you start disconnecting things. Most importantly, when you open the driver-side door, the brake actuator pressurizes. You don't want this happening when things are disconnected!

b) remove the wiper cowl and lower metal pan:

c) remove the faulty actuator by loosening the brake line nuts with the proper tool: a flare nut wrench. Do not try to do this with a regular wrench. If you do, you will strip the nuts. I forget which size the nuts are, but I think it may be 12mm. I purchased a set which included 7mm through 14mm for about $25.

d) Once the brake line nuts are loosened, go inside and get your head on the floor upside-down so you can remove the 4 nuts holding the actuator to the firewall. I think these are 14mm. Tip: be careful not to let the nuts drop to the floor when removing: there are several nooks and crannies they can get lost in, and there is virtually no visual access to these areas. One of my nuts fell into the steering column access in the floor/firewall, and I had to use a magnetic pickup tool to fish it out (luckily).

e) Disconnect the actuator from the brake pedal. There is a locking pin that just pulls off - it does not need to be bent or mangled to remove, which is important because you will reuse this part when re-attaching everything.

f) The actuator is now ready to pull out of the engine bay. Gently pull the brake lines out from the actuator so that it can be pulled out. You will spill some brake fluid at this point (at least I did). Make sure the concrete under the car is protected and have rags handy. Do not get brake fluid on the car's paint because it will eat it very quickly. There is limited access here and the actuator was fairly difficult to remove. The brake lines and other parts are in the way. Do not bend the brake lines - they need to line up correctly when you install the replacement actuator. Try rotating the actuator up and out.

4. Install the replacement actuator in the reverse order. When re-attaching the brake lines, start the nuts *carefully* by hand. You do not want to cross-thread the nuts. They should go on at least a full turn by hand before a line wrench is involved. Once all of the brake lines are in place, use your fingers to tighten them as much as possible because this is easier and less chance of cross-threading compared to using a line wrench. Now that the brake lines are all hand-tightened, go inside the car and attach the actuator to the firewall and brake pedal. Then, go back to the engine bay for final tightening of the brake lines with the line wrench. Do not over-tighten or else you may strip the delicate aluminum casting of the actuator.

5. For the above work the dealer quoted me about $4,300. All that's left now is a complete brake fluid flush to get rid of all existing fluid (and newly introduced air) in your lines, as well as the existing fluid in the replacement actuator. In other words, you are essentially home free at this point because many, many garages can do a brake system flush for you for a very reasonable cost. However, you can now save a bit more money by doing the brake fluid flush yourself. This process has been detailed many times before, so I won't bother to do so again here. The only thing to note is that the Techstream software has an additional option when flushing for when you replace the actuator. I guess this option goes through some additional steps.

 

This seems to be more common than I 1st thought @RightOnTime


aka Masta S
https://www.facebook.com/100004124476496 Sean Dasselaar (@sfv41901) • Instagram photos and videos Sean D (@sfv41901) on Twitter

 

Thanks for putting together the write up. Are the Extended Instructions step 1-5 for the ACTUATOR or ACCUMULATOR? I know people have had to replace one or the other before here.

 

The instructions are for the ACTUATOR. However, they could mostly be used for the accumulator as well, because if you can access the actuator, then you can access the accumulator (beneath the actuator).

 

Should you ever have a need to replace the ac·cum·u·la·tor, just look for the PDF of the recall "D0H" campaign instructions (that's a zero in the middle, not a Homer Simpson quote). Instructions don't get any better than that. I think it was reposted recently here somewhere.

-Chap

 

Is the reprogramming something that can be done with Techstream? Bought a salvage actuator + accumulator combo from a 2015 with 50k miles. Only the actuator had failed, but figured why not replace the accumulator while I'm in there. Big mistake, what a headache compared to just replacing the actuator and letting it ride.

Does it still need to be reprogrammed if replacing both parts together? And will I need to bring it to the dealership for that?

 

Hopefully someone with direct experience will comment, but in the meantime...

I have not done reprogramming myself, but it doesn't look like a big deal if you have a current copy of Techstream.

Note that the ACTUATOR has an integrated ECU that will need to be reprogrammed if the part number is not an exact match for your car. In contrast, the ACCUMULATOR does not have an integrated ECU and no programming needs to be done.

A poster at the beginning of this thread had his ACTUATOR reprogrammed by a garage and it cost $60.

Is the 2015 accumulator part number the same as your 2010?

 

Here are the part numbers (for my old & new actuators, at least, both accumulators are 47070-47050):

2010 Actuator: 47210-47140
2015 Actuator: 47210-47470​

I'd be surprised if they actually fixed the problem on the 2015, just hoping to have a 5 year head start before it happens again.

I found T-SB-0363-10 posted on another thread that shows a 2010 Prius reflash procedure, so hopefully it will turn out to be something similar. I'll post a follow-up this weekend once I get to that point.

 

I wanted to ensure keeping a copy of your #65 post, made a pdf:

 

That's good news that both accumulators are the same PN.

I've previously inquired in this thread about known failures of 2012+ actuators, but so far I'm not hearing anything. Seems to me that the new PNs might indicate an improved part. But the updated PNs could also just indicate a different software version due to different years having slightly different options that would affect the ABS software (e.g., OEM wheels have changed over the years). The different PNs *within* a model year definitely indicates only different software versions for different wheel sizes.

Keep us posted on your progress - I'm definitely interested!

 

I would also bet lunch that they simply improve the software from year to year, but only some of the improvements are significant enough to be advertised in a free recall (like the 2010 regen-to-ABS handoff) or a come-in-and-pay-us-to-update TSB (like the quacking).

I would strongly suspect that if you put in a newer unit, connect it to Techstream, ask it what its calibration number is, and it is any of the newer calibration numbers listed for your wheel size (15 or 17 inch), it will probably work just fine, and maybe have some obscure improvements over the older version.

Heck, even if you had the software for the wrong wheel size, I don't imagine you'd be likely to notice ... how many owners swap in different-sized wheels without reflashing their brakes?

But I don't know, maybe Toyota has written more about the calibration compatibility, in a document I haven't stumbled on.

-Chap

 

Could that be?

 

Not just could be but is; see the different calibration ID numbers in #29. Why ? It's just the way it is....

-Chap

 

The reason I recommend you get the same number you take off is because the sky is the limit on the software code changes that can be made. All the computers in the car share the same communication buss just like any car. If they have to share any code then any different code can cause the computer throw an error. The last thing I would want to do is go to the dealer and try to talk him into making a salvage yard part work. That's like going there, opening your wallet and saying "take what you like now that I have screwed you out of that 4500 dollars you quoted me". I don't believe the dealer reflashed anything for 60 dollars when they charge 75 just to do a diag on the car. They have to pay the bills too and I understand that but we have to find a happy medium. I am a IT guy by trade, and have worked on many different cars. Here is a picture I keep handy for people to see whats actually inside an ecm. I know this brake system isn't as smart but it certainly contains a lot of processing power. Zoom in on this puppy as I think it looks kind of cool.

Again this is not a brake actuator, its just an example of what can be done with a car part, and when you are dealing with black boxes you don't have a clue what the programmers have put in their code. If you zoom into this picture, the thing I find most interesting is they don't even package the chips, they just wire bind it to the other circuits.

 

Coincidentally, Toyota released T-SB-0079-18 during my 2-day TIS subscription related to C1391. They recommend replacing both the actuator and accumulator. Do they think both will end up having problems, or just not confident in the tech's figuring out which is really at fault?

 

Interesting and timely find! I see three things to note from that TSB:
- they say this only applies to 2010, but clearly this issue is also present on 2011
- they list new PNs to replace the original PNs. How recent are these new PNs, and were they revised specifically to address this issue? Obviously this is way more expensive than buying used.
- They list a new firmware (calibration ID) for the actuator. The firmware jumps from F152647108 (which was current as of TSB 0363-10) to F152647760. I wonder if this new firmware can be applied to older actuator PNs?