brake, abs, (!), VCS lights on

That's usually not the way you want to think about it. Coincidences do happen sometimes, but usually when you have a problem and several codes show up, they are not telling you about five different problems to track down; they are telling you five different aspects of the elephant you're trying to find.

Think set intersection; remember drawing Venn diagrams? One or two of those codes would leave you a large space of possible problems to try to consider and rule out. Narrow down to the situations that could trigger all of those codes, and you've zoomed in on a much smaller space of possible causes.

One key is that the little "fortune cookie" one-liner descriptions that go with the codes do not give you enough information to follow that procedure. Where you do find that information is in the "detection condition" boxes in the Repair Manual on the pages for those codes. The "detection condition" lists the actual things the ECU has to see happen to make it set that code. Once you have those all in front of you and start drawing a picture where those things all happened, you're on your way to pinning down the culprit.

A couple more points: read carefully the detection conditions for the code about voltage; you'll see it doesn't refer to the aux battery at all. It is about voltages as measured at or inside the brake ECU, and the suggested areas for investigation are all things like wiring, connectors, relays, fuses.

Also be careful with codes about accumulator pressure drops, as the causes can be in the accumulator or the actuator, irrespective of what the fortune cookie says. (That's more a warning for Gen 1 or Gen 3 folks who might be reading along; in your Gen 2 the accumulator and actuator are part of the same assembly and not separately available, so it kind of doesn't matter.)

 

Hello, first time poster. I've read a lot of the threads and now my brain is mush and I'm in desperate need of assistance.

I have a 2005 Prius with 220k on it. No accidents. replaced hybrid battery at 153k miles. Did both rear wheel bearings at 182k. By necessity I learned how to change my own inverter pump in June at 216k and I changed my 12v battery with a new Toyota one at the same time. 6 days ago the "brake" "(!)" VSC ABS lights all came on. Only once during the last week did a 10 second sustained beep sound occur. I haven't noticed any issue driving it, but yesterday when I backed out of my driveway I noticed brakes were sluggish in reverse. Going forward still no issue whatsoever. My brake fluid is normal level, the inverter is working and it has fresh fluid from when I did the replacement.
I used two different code readers and there are no codes. Used diagnostic mode to check 12v, it showed 11.9 so used a charger on it and the lights still stayed on.
After lots of reading I fear an actuator issue and those all show to run 1k bucks which of course I can't really afford. But, if that's the case, wouldn't there be at least one code being thrown to read?? I'm not a car gal at all but, I'm starting the learning process so, any and all guidance would be greatly appreciated as I seem to have reached dead end. Thank you

 

I would suggest that you look on amazon or ebay for a copy of Toyota Techstream with a mini VCI cable and install it on an old windows laptop. This can be tricky to install but gives you factory level access to all modules on the cars for codes and data. OR find someone with a better scan tool. If you have warning lights on the dash AND a warning beeper, then there should be codes somewhere. Some of the lights and codes are saying "hey, there's a code in another system".

Many generic scantools can only talk to the engine computer. I would want to make sure that I can "talk" to the the ABS computer before believing that it doesn't have any codes. Without a full check for codes then you/ we are guessing.

If your problems continue, then please don't drive the car as what you describe does sound like brake actuator failure. Complete failure will leave you with no boost (hard pedal, long stopping distances), no ABS, no regenerative braking (lots more use of the gas engine, low mpg, and stress on the high voltage battery), and no rear brakes at all.

Good luck.

Posted via the PriusChat mobile app.

 

Thank you for the insight. I feared as much so haven't been driving it. I found a disk and cable on Amazon for around 70$, I'll see how it goes. While it had lots of reviews and was highly rated, seems pretty sketchy that it's required to turn off virus protection in order to use it. I'll wipe my old laptop and see if it works. Thanks again