ABS lamp and beeping - prognosis?

Get it scanned for codes. You may have issues with the actuator

 

The OBD2 reader that you used did not get the codes from the brake system, but you need them.

A mechanic with Toyota Techstream software can retrieve them, or you can, using just a short wire and counting some blinking dash lights. You can search this forum for lots of posts about blink codes and the Tc and CG terminals, for how to do that.

There are on the order of a hundred things that can set codes in the brake system, but only about half a dozen that also set off the alarm beep, so we know it's one of those.

If you had a Gen 2, a lot of the possible culprits would be combined into what's basically one replaceable assembly, so after ruling out simple things like wiring and relays, there wouldn't be much question what to do next.

But in a Gen 1, the components potentially involved are in three different replaceable assemblies, so it's in your interest to narrow down the problem a bit more. It all starts with those codes.

I wrote an old post a while back that was really about diagnosing ECU-monitored systems in general, but I happened to use the Gen 1 brake system as the example, so it might end up being particularly useful to you here. (One thing you'll notice is that even for "ruling out simple things like wiring and relays", if you're doing that without the help of the codes and the manual, you're going the long way around.)

-Chap

 

My thought is that you need a new brake booster pump. I've been thru this and the symptoms match yours. I replaced mine with a used one from a junk yard and bled the brakes and haven't had any troubles since, it's been over a year. From Toyota, it's about an $1100 part. I got my used one at a pick n pull for $25. Pays to check all the sources. Ebay, Amazon, etc. I know you're in OZ but it would probably be worth having a used one shipped from the US.

 

Ok, getting somewhere now. The repair manual is where you find more information than in those one-liner fortune cookies that people throw around for those codes. The manual describes what are called the "detecting conditions", namely, what actually happens in the car to make those codes be set.

The "low pressure malfunction" fortune cookie seems mostly connected to the pressure monitoring signals: the computer will set the code, for example, if it sees both the low-pressure and high-pressure switch signals at the same time. There are five such conditions listed in the manual. One of them is just that the low-pressure signal stays on for more than 60 seconds while the ECU wants to pump it up, in which case the pump could be faulty, or could just be receiving bad power. There are six pages in the manual of troubleshooting steps you can follow for that code to pin things down.

The detecting condition for 64 is that the different pressure sensors in the system give different readings for 1 second or more while you have the pedal depressed. That could indicate a wiring issue, fluid leakage, or a problem in the actuator (note: in a Gen 1, the actuator is not in the same assembly with the accumulator/pump; they're different items). There are only a few checks to be made there, but they're simplest with Techstream, where you can watch the readings from the different sensors to see what's funny about them.

Replacement of the Gen 1 accumulator is a long knucklebusting job (more so if you don't want to have to evac and recharge the A/C, which is in the way). In some cases it'll turn out to be the problem, but you'd probably hate to do it first and have it not be.

-Chap

 

Yes, it does draw a bit of blood. Lately everything I do on cars does, tho.

 

What are you using to scan for codes. Repeated postings that say "no fault codes" when there are clearly warning indicators usually mean the poster isn't using a Prius-capable tool, which slows down getting information about the problem.

By the way, the voltage reading on the MFD is handy, but usually a good fraction of a volt low, just because of where the reading is taken. That reading probably means you'd be seeing 12.2, 12.3 or so with a meter at the battery.

-Chap

 

In Gen 1, a lot of the ECUs still had fallback code reading abilities based on a jumper wire and counting light blinks. (Some of those were kept into later generations; as late as gen 3 at least, light blinks still work for brake codes, and I think airbags too.)

But Gen 1 had a couple of ECUs that lacked any blinky-light fallback and can only be read over the diagnostic bus: the HV ECU and the Battery ECU. (Three, if you count the steering ECU, which has a blinky-light fallback feature but no light wired to it.)

So if you're getting the car-guillotine symbol and you can't retrieve the codes responsible, chances are they'd be originating in the HV or Battery ECUs (the steering ECU would light the PS symbol on the MFD instead).

But there are hundreds of possibilities there, so it's not as if I can just say "well, if it's probably coming from one of those two ECUs, then it must be X".

Reading the codes with Techstream would help a lot.

I am not one to write things off as low-voltage artifacts much of the time (and certainly not based on a reading of 11.7 at the MFD). Certain codes won't come back after clearing until the detecting condition happens again, which could be right away or not right away. I would just continue trying to narrow down possibilities based on the information the car wants to give you.

-Chap

 

2001 Factory Service Manuals will work just fine for all the Gen 1 Priis. You really need to get the Techstream setup. It's available on Amazon.com.au. Here's the link: Techstream TIS V12 Mini VCI USB Interface OBD2 Car Diagnostic Cable for Toyota: Amazon.com.au: Electronics

 

It can be installed in Win XP and later laptops. I have mine in an old surplus XP machine--dedicated and never gets connected to the internet. Got mine for under $35 us$. It's a Dell, Dude! Anyhow, go with whatever Chap says. Torque has pretty minimal capabilities for Prius, I have it for another vehicle, but never use it on either my Prius or my Porsche.

By the way, there are two main Factory manuals, and a bunch of other accessory manuals. Bishco publishes authorized copies of the factory manuals. In the US, they are about $100 for both main manuals plus shipping from Rock Auto.com I don't know if they ship to Oz. They would be superior to scanned copies, tho.

 

What's the name of this scantool? Can you provide a link? Want to take a look at it's features.