How to disable the ABS high pitch alarm? 2002 Prius

You can get a used one at Amazon. $300, just fix it. Or on ebay for even less. Power Brake Booster Fits 01-03 PRIUS 8353863 | eBay

Power Brake Booster Fits 01-03 PRIUS 12482927 | eBay

 

Oh and I think 3prongpaul is in denver and could install it for you.

 

Power brake booster is the part you need. The booster on a classic Prius is a electric pump, not the vacuum assist found on conventional brake systems.

 

I hate to be the stickler on nomenclature again, but Gen 1 also has both a "booster" and a "booster pump" and they are completely different things. They get confused all the time, and parts vendors will nearly always confuse them, so you need to be ready for that, but we can at least do better on PriusChat. (Even some Toyota publications contribute to the confusion.)

The "booster" you can't buy separately anyway. It is nothing but an extra hydraulic chamber formed in the back of the master cylinder along with a rubber disc and reaction valve. It probably isn't your problem.

The "booster pump", a/k/a the accumulator assembly might be what you need. ("Booster pump", in parts-catalog comma-speak, is "pump subassembly, brake booster"). It is mounted over on the passenger side of the firewall in Gen 1 and is a lot of labor to replace. The official procedure involves evacuating the A/C, then moving some A/C pipes that are in the way, then recharging the A/C after the job.

You can find a post by PriusChat member rlin78 who found a way to DIY it without disturbing the A/C, but it took about ten hours.

With that kind of labor plus the cost of the part, it is worth making sure the part is what's needed first. Do you hear any of the usual accumulator pump sound when you turn the key on? (Do you remember what that sounds like, from back when it was working?)

The alarm you are getting could be because the pump is not pumping at all, or not pumping effectively enough, or not keeping up with an internal leak (which could be elsewhere in the system). Not pumping at all, or effectively enough, could be the pump itself, or the electrical supply to the pump.

I once wrote a post specifically about all the diagnostic info the Gen 1 Prius gives you about the accumulator pump, so it would be worthwhile to pull the brake system codes. That can be done with a fancy code reading tool, or just with a short piece of wire and counting light blinks.

-Chap

 

You're right Chap. I don't even mind when you correct or add to my post. Feel free anytime.

Those booster pumps or accumulator pumps that I linked to would be the correct part for the OP, tho.

 

Did we ever find a way to disable that pesky alarm though? I had my actuator replaced twice and it did not solve my issue. No more money to spend on it at this point. Having the alarm sound disabled would bring me a level of bliss that cannot be put into words.

Yep - it'd be masking the issue but like the OP the car otherwise stops fine. I'd love to troubleshoot it further but number one priority is turning off the sound.

Thanks!

 

That, in a nutshell, is why I'm always on like a broken record about the importance of finding the cause of the problem before reaching for parts to replace. If the parts are cheap, that's one thing, if it gives you a quick way to rule out the part as the problem. But something in the price range of a brake actuator, and then you replace it twice, just leaves you out of money before you have found or fixed the problem.

The alarm isn't telling you the car doesn't stop fine. The alarm is telling you to expect that to change. The other drivers on the road around you can't hear your alarm, so they don't know of the danger.

At this stage, the best way to silence the alarm is to drive another car, or a rental, until you can get back to fixing the brakes on this one.

 

OK. Plan B: troubleshooting.

Errors: C1254 and C1256.

Symptom: Brake pedal noticably different when pushed (slightly harder.) Brake/ABS light is on along with an invulnerable alarm noise every so often.

Steps thus far: replaced Brake Actuator pump. Same errors generated. Replaced actuator second time and once again, same error codes generated. Mechanic tested the current to the actuator and said it tested fine and is not defective. He believes it is an "electrical issue" elsewhere, gave up, and sent me on my merry way.

Suggestions welcomed. Thanks.

 

Do you have a laptop you can run Techstream on to read back the data from the brake ECU, and access to the repair manual for the troubleshooting info? The direct source is techinfo.toyota.com, but Elektroingenieur often posts about free services (Chilton Online?) that might be available at your local public library.

The key first step is looking up the "detection condition" for each code you've got. That isn't the same as the sort of one-liner fortune cookie that you see next to the code on a printout. The fortune cookie is next to useless. The detection condition states exactly what the ECU has to be seeing happen, to make it set that code. Sometimes there are several possibilities. With Techstream, you can often retrieve a "freeze frame" of all the sensor readings at the time the code was set; line that up next to what the detection condition says about the reasons the code can be set, and a story starts to emerge. There will also be several pages there, usually, of ideas for further tests you can do to fill in the story's details.

To be a little strict about terminology: there are two names for parts in the Prius brake system that are very similar, and people very often mix them up: accumulator and actuator.

In a Gen 1, the accumulator (which includes a pump) is over at the passenger side of the firewall, under where the brake fluid reservoir is. The actuator is more mid-firewall, hard to see behind the engine; big square box with a bunch of steel brake tubes running in and out. (And the master cylinder is another separate part, over where you expect it to be, lined up with the brake pedal on the driver's side of the firewall.)

From your description, I'm thinking the accumulator (the part with the pump) is the thing that's been replaced twice, am I right?

Knucklebuster of a job, too, that.

 

Have same issue with this 2001 I just bought, while the brakes are hard (no power), they work ok, if you put the car in "B", it slows up quite well. In any case, I will be replacing the brakes with a normal manual brake system, and would like to just delete the noise so I can drive it until the modifications begin. Which device is producing the noise? I noticed the ABS relay was missing, as I tried to remove the ABS fuses and it had no effect, so I'd guess the ABS system is not making the noise. Appreciate any help.

 

Here is location of the buzzer to help someone else.

 

The hole is on the right side of the wheel between the break and gas pedals. A temporary fix until you get it fix at an auto shop.