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So my highlander has the dreaded accumulator pressure low, internal leak code. I'm sorta of puzzled what part that needs to be replaced. Is it the block actuator thing or the pump / accumulator? I have access to Techstream and would like to fix this problem on the cheap.

I don't wan't to throw a 800 dollar part at the issue just to find out i need to spend 1000 more. I hear that it could be the pump or the actuator assembly. I read about the active brake test in TechStream but don't fully understand what exactly i am looking at/for. Can some one explain the troubleshooting process that i go though in the Tech stream software?

I really cant afford to spend 3k to get this issue fixed right now, but i can afford some used parts and a bit of tinkering.
 

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If any one has this same problem here is how i fixed the abs system. This can be done as a DIY, If i can do it you can. You will need a special tool to bleed the air from the system after replacing components. You don't have to spend the $2400 for an actuator and pay Toyota techs tons of money.

If you have C1391 error only it is %99.9 likely the valve body leaking accumulator pressure back into the reservoir. You likely do not have to replace the booster pump. Assuming you find no external leaking. You can replace the part with a rebuilt unit. I found a guy on eBay that rebuilds the valve bodies and fixes this internal leaking. It was $870 and well worth. Andy is really passionate about helping. I know some of you are going to say "But ozzy thats not a servicable component. That wont work." The alternatives to me are unacceptable, a used part costs about as much as rebuilding...

Installing this part was not difficult. Use a line wrench and carefully hand tighten every thing so you dont cross thread and Don't over tighten. Follow along with techstream to bleed the brakes then clear the error codes, easy peasy. It took me about 5 hours in research and about 2 to fix the issue. I was into this $35 for a mini vci cable, $12 in DOT 3 and $870 for the part and shipping. Less then a grand.
 

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..

If any one has this same problem here is how i fixed the abs system. This can be done as a DIY, If i can do it you can. You will need a special tool to bleed the air from the system after replacing components. You don't have to spend the $2400 for an actuator and pay Toyota techs tons of money.

If you have C1391 error only it is %99.9 likely the valve body leaking accumulator pressure back into the reservoir. You likely do not have to replace the booster pump. Assuming you find no external leaking. You can replace the part with a rebuilt unit. I found a guy on eBay that rebuilds the valve bodies and fixes this internal leaking. It was $870 and well worth. Andy is really passionate about helping. I know some of you are going to say "But ozzy thats not a servicable component. That wont work." The alternatives to me are unacceptable, a used part costs about as much as rebuilding...

Installing this part was not difficult. Use a line wrench and carefully hand tighten every thing so you dont cross thread and Don't over tighten. Follow along with techstream to bleed the brakes then clear the error codes, easy peasy. It took me about 5 hours in research and about 2 to fix the issue. I was into this $35 for a mini vci cable, $12 in DOT 3 and $870 for the part and shipping. Less then a grand.
Can you link the supplier you used to get the part?
 

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Actuator Assembly Replacement at Dealer

I had that squeaky/vacuum-like noise really bad when I was at a stop with my foot on the brake. This is a primary vehicle for my children so I had to suck it up and pay for the replacement. $2400 later :wtf:. A GM SUV is sounding really nice right now :|:|
 

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Important for people to know if you have internal accumulator leak you need to stop driving or the accumulator pump will burn up its not desined to run continually if you have a high pitch alarm in the car that wont shut off the pump is fried and unrebuilable they cost about 800 great post about the place that rebuilds the accumulators thanks gearhead not enough of us
 

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I was having the same problem and the ABS pump was cycling every 10-15 seconds. I decided to just flush the brake fluid with some brand new fluid . Now, the pump would only cycle every minute. So, the solution might be simpler than we thought. This is the second day. Will see if it actually fixes the problem.
 

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My wife's 2008 is at the dealership now. Been there since last Thursday waiting for parts. Pump was bad as well, I guess.
$2,600 and the warranty is just one year.
No one should buy one of these used until Toyota steps up and takes care of this defect.
 

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3rd day after the brake fluid flush. Brake pressure held for more than 2 minutes yesterday. I would say the problem is fixed for $9 and 20 minutes of my time.
 

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3rd day after the brake fluid flush. Brake pressure held for more than 2 minutes yesterday. I would say the problem is fixed for $9 and 20 minutes of my time.
Edward - can you please update again? Have you had to do anything more on this yet? We're getting a C1391 error and have our fingers crossed we can do a brake fluid flush/bleed to see if that takes care of it.

Ozzy - how did you determine you would need to replace only the actuator assembly and not the booster pump? I believe c1391 is the only code we're seeing but the dealer wanted to replace both.

TIA. This is such a disappointing fail. Have loved my HiHy up to now.
 

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3rd day after the brake fluid flush. Brake pressure held for more than 2 minutes yesterday. I would say the problem is fixed for $9 and 20 minutes of my time.
Edward - can you please update again? Have you had to do anything more on this yet? We're getting a C1391 error and have our fingers crossed we can do a brake fluid flush/bleed to see if that takes care of it.

Ozzy - how did you determine you would need to replace only the actuator assembly and not the booster pump? I believe c1391 is the only code we're seeing but the dealer wanted to replace both.

TIA. This is such a disappointing fail. Have loved my HiHy up to now.
Still doing good. The booster pump sounds quieter. And, now, the pump would not even turn on when I open the driver door even after sitting in the garage for 2 days. I can force it to turn on by pressing the brake pedal. It will then turn on for 2-3 seconds and stay off until the 2-minute timeout.
 

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3rd day after the brake fluid flush. Brake pressure held for more than 2 minutes yesterday. I would say the problem is fixed for $9 and 20 minutes of my time.

I'd like to caution here.
HiHy has drive by wire brake by wire system. As such, brake fluid flush has to be done with scanner, to move valves in brake actuator. By no means that is $9 fix. Trying to flush brake fluid conventional way may result in damage to brake actuator. Dealer charges approximately $150 for procedure.
From my 8 years with hybrids, I do not believe brake actuator has to cycle continuously, no matter what intervals, shorter or longer. It should prime at start up and after shut down, that's pretty much it. Any cycling action or triggering it with every brake pedal touch points towards problem with the system.
 

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Still doing good. The booster pump sounds quieter. And, now, the pump would not even turn on when I open the driver door even after sitting in the garage for 2 days. I can force it to turn on by pressing the brake pedal. It will then turn on for 2-3 seconds and stay off until the 2-minute timeout.
Thank you for that update. We did a bleed (with a scanner) yesterday and have since had it on the road maybe 30 miles. No lights on yet and I'm not hearing the pump run nearly as much. The flush seemed a bit off so we might try flushing it again next weekend or before in case the lights come back on prior to that.
 

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Thank you for that update. We did a bleed (with a scanner) yesterday and have since had it on the road maybe 30 miles. No lights on yet and I'm not hearing the pump run nearly as much. The flush seemed a bit off so we might try flushing it again next weekend or before in case the lights come back on prior to that.
I took a long camping trip towing a travel trailer over the weekend. Everything works great.

Did you get a chance to redo the flush?
 

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I took a long camping trip towing a travel trailer over the weekend. Everything works great.

Did you get a chance to redo the flush?
Good to hear you are continuing to have success.

Yes, we flushed the brakes again. I found more detailed instructions that help step through flushing the actuator and master cylinder and it was a much more thorough procedure. Unfortunately I think all that activity may simply have stressed some components because now we're hearing the pump run more frequently again. Perhaps we should have left well enough alone. Time will tell.

In my search I found lots of threads on priuschat about people diagnosing and dealing with ABS actuator issues. Given what I've read I wouldn't be surprised if our actuator is on the way out and it's only a matter of time. We are considering just replacing the actuator after all. Access is easy and should be a straightforward swap.

Since this is a very early 2008 (engine stamp is actually 2007 I believe) I have a feeling this actuator is not unlike the others that Toyota has replaced under warranty extensions. I may follow up with Toyota customer service to see if I can get reimbursement for the part.
 

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It's brake actuator. Not ABS actuator. I have not yet seen ABS block failures. Brake actuators, unfortunately, ongoing issue.
Thank you for clarifying.

By the way I was going to come back and add that since bleeding and clearing codes the warning lights haven't reappeared. But no kidding just as I was thinking that the lights came back on.
 

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As I mentioned, actuator should not be cycling at any rate, longer or shorter cycles. It primes right after Start and right after shut down. I think, it's releasing pressure after shut down. But that's about it.

Sorry.
 

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Ozzmundo or anyone else able to share tips on replacing the HiHy ABS Control Unit (actuator)? Our replacement part just arrived so we'll be doing this shortly. We've done jobs on this vehicle like spark plugs (yes even the rear ones) and wheel bearings, but am a little intimidated by the brake system. Anyone have a step by step to share or care to help map out a plan?
 
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