Cannot complete replacement brake booster air bleed procedure

50 amps??? OUCH! That is WAY too much for the 12v battery. 5 amps is enough.
What device are you using for the procedure? Is it an aftermarket techstream cable? If so, that is
likely your issue. It's common. Some say there is a certain cable to buy to get it to work.

alteck has a tool, I'm not familiar with it, but others are. I have the D8Tools device that is very good.
I'll be using it when I do the brake job in the future.

 

Did you buy a new or used part?

 

I seem to remember someone saying the car had to be on, but not ready? I'm not really sure.
It was a while ago.
Perhaps search prius chat for that procedure and you'll find the issue.
A lot of people seem to have a similar issue. Usually it's because of a pirated copy of techstream,
and/or cable.
Maybe try it with the parking brake off? Or the opposite of where it is while your bleeding?

I think you can just do a regular bleed procedure, instead of going through the whole thing again.

I don't know about the other sensors. But since you have the scan tool, you want to check why
they are showing zero, and if that is normal or not.
Obviously, you should check all the wiring to make sure nothing is damaged.

You can get the Xtool D8 (and now D9) for less than $800.

 

If this is a gen 3, the ECU is included in the actuator assembly.

Didn't see this post earlier. No ouch. 5 amps is on the battery label for a charging current.

The car is IG ON while you're doing the bleed procedure, and the car's electrical equipment is drawing power. At a Toyota dealer, doing any sort of long procedure where the car has to be IG ON, they'll have something like this hooked up to the battery:



It won't be set for 'charge' mode, but for 'power supply' mode. It's supporting the power being used by the car, so the 12-volt battery does not lose charge.

 

I had this problem on a CT200h. There were some fault codes about steering angle sensor and zero point thing. Forgive me for not knowing the exact codes. I purchased a second hand abs module and pump. After replacing the unit i could bleed the system right away. I assume your problem lies in the new unit. Double check the part number

 

Curious about this problem. Following...

 

How did you bypass the 125a? Can you post a pic?

That certainly is not right. There is an "Accumulator Sensor" (accumulator pressure represented in volts) you can graph.

Based on the attached replacement video, that sensor should start the pump around 3.1v and stop it around 3.8v. One of your techstream screenshots shows it at 3.58v.

It might help isolate the problem if you know what your pressures are doing.

Accumulator Sensor 3.1v - 3.8v

Initial startup after bleeding. Each brake depression causes about 2 seconds of runtime after the first cycle.

The repair manual pdf on the Accumulator Sensor shows a range under certain conditions of 2.9v-4.2v

This video fairly comprehensively documents the replacement bleeding and calibrations.

 

It looks like the pump is giving you good pressure but it is not dropping hardly at all on brake activation compared to the graph of a known good in the post above.

1. Do you have brakes if you try to drive it?

2. How did you verify the new brake booster was correct?

3. Did you buy the brake booster from a Toyota dealer?

4. When you blew the 125a fuse did you also replace around six other fuses?

5. Was the car functional without codes after the 125a problem was resolved?

It looks like your 125a bypass has no fuse. I think I would add one at some point that functionally separates the white 12v incoming from the inverter connection.

However the lack of a 125a fuse is not the issue with the brake booster.

Finally if everything else checks out, I would get it to a dealer and let them do the replacement bleed and calibration.

 

George Jung, post 14 above:

Thank you for the help.

1. Yes. Ive been driving it in this state since. July. intermittently, the cruise control will stop working after ive been messing with things, but happens to come back the next time i go under the hood and mess with things. I cant tell you exactly what i did when it stops working, but that has happened 2 or 3 times now. One time I did skid out of control on the freeway when i was changing lanes and then traffic suddenly was coming to a stop.

When it stops working? And comes back? A failed brake booster loses abs, skid control, regen, mpg and has a hard pedal. When it "starts working" do the dash lights clear, power brakes return, etc?

2.+3. I used the part finder thing based on year and model on Toyota.com, then took the part number it told me and bought it from bamauto.com. When i was removing the old one. I noticed it looked newish, then i recalled that i believe the old owner did say he had replaced the master cylinder before. Im not sure if he did the pump also or
just the master cylinder. The part number on the mastery cylinder was the same. last night I put back on the one that was on there before.

Bamauto.com? I don't believe that is a Toyota dealer and seems to be a dead site now. Dealer sites have a format like "autoparts.hoovertoyota.com" where the "hoovertoyota" portion is the name of the dealer. There are a couple of exceptions like "autoparts.toyota.com"

The Toyota part number is different by tire size in the same year and is different between hatchbacks and Prius v's. In addition the number on the housing is not the actual parts number, it's a housing number which is the same across many part numbers. Used sellers often don't know this and advertise it incorrectly.

Do you have the Toyota box with a label the newest brake booster came with? It's the number you want to verify.


4. No, that was the only one i believe. I dont recall replacing other fuses at the time.

Normally everybody that blows a 125a fuse also blow six or more other fuses. You could still have a blown fuse but they might be smaller regular fuses.

5. Yes i was able to bypass the fuse in the parking garage of the ferry terminal, then drive back 5 hours to vegas at 10pm on sunday night, after spending like 8 hours figuring out what was wrong. i took like 3 uber trips to auto zone while my poor girlfriend waiting in the car. I dont recall any other issues appearing at that time. I have the replacement 125amp link. I do plan on replacing it soon. I was possibly going to do it today but thats probably not going to happen. Im going to have a couple free days later on this week, im going to get that done then figure out these wiring diagrams and get to the bottom of this brake issue.

I feel there's got to be a bad wire or something somewhere. When i replaced the engine i did snag that harness that runs on top of the transmission, next to the radiator hose coming out of the engine block on the right side. I had to repair wires on the mg1 sensor, and right now im tracing down a bad wire for the MAP sensor. IDK if that harness is at all related to the one going to the ECB, it doesn't look like it.

Blown 125a, replaced engine, modified/ repaired wires and now an intermittent brake booster. It does make wiring, grounds or network buss problems more of a possibility.

Im not going to take it to the dealer. Im going to fix this myself even if i have to replace every ECU in this POS.

 

I love it! My local dealer told me recently that there was no way to check health of the hybrid battery. It just needs to be replaced if the relevant code shows up in the system. Boneheads!

 

That's kind of not totally as boneheaded as it sounds. When a P0A80 code shows up in the system, it's the result of computations the ECU is able to make based on real-time monitoring of a bunch of battery performance parameters and driving conditions all while you operate the car.

It's not that you aren't able to measure those same parameters with instruments, or peek at snapshots of them with a scan tool, it's just that what the P0A80 code tells you about the "health of the hybrid battery" rests on a more solid foundation of real-time measurement and computation than anything that's practical for you to do to second-guess it.

That's why at the dealer, where economics weigh against spending a lot more time for small hope of a different outcome, they are inclined to respond to the P0A80 "replace hybrid battery" code by simply doing that.

 

Yes, that makes sense. But let me present an anecdote. Take a look at this video (start @2:50):

.

for the complete diagnosis a tech provided at a Toyota dealership. There are people who would do these things, and others just want to throw parts at it based on what ECUs say. I understand the economic reason for doing so, but it's so wasteful. My problem is primarily them being drones and not answering any questions in depth.