Abs vsc and (!) light turning on and off. While on brakes don’t work well.

And what are your codes when this is happening That's what you need to know More than likely is the same as all of these generation twos and the accumulator pump assembly is fubar generally it's pumping a lot or most of the time You hear it very well when turning the car off or walking up to the car it starts whining and pumping and whining and pumping the minute you touch the door things like this or the dead giveaways I drove my car for 2 years like this My pedal was not spongy or anything actually worked very well until you pounced on the brakes very quickly then they would lock up all four wheels and the car would slide just like an old track car very predictable actually 2 years and a few months into this business one day I stepped on the break and only one front caliper was working the next day I changed the accumulator pump all the lights went off the brakes work perfectly they've been that way for I don't know 10 months now so this is probably what you will go through too I don't think this is an indication of bad wheel sensors or plugs to those wheel sensors It's usually the pump and accumulator assembly as of last week in Central North Carolina If you ordered that part on Rick Hendrick.com and picked it up at the Toyota dealer of your choice in the network the part was $1,428 if I walked in and purchased it at the parts counter which they don't have in stock when I came back to get it it would be 1728 so you purchase accordingly You can buy them out of junk cars now you see people trying to get $350 for them or more If they can't provide me with the necessary information to my questions I don't generally buy those because a lot of people now are all of a sudden Prius experts and just buying jobs of parts and putting them online not knowing whether they work or not because you're just out your money that is the key today most of these people selling parts or fly by nighters that are just trying to make a quick buck off the internet off of people's ignorance so beware of these things if you don't know the right questions to ask by the new part save yourself a bunch of trouble It's not that hard to change but you know people just turn things into a big pile of poop if they're allowed.

 

Hello and welcome to PriusChat!

The brake control (ABS) ecu is detecting problems and alerting you by turning on warning lights. The fastest way to figure out what's going on is to retrieve whatever codes are stored. One way is to (carefully) jumper the 2 correct pins on the OBD2 data connector under the driver's dash area, turn the car ON, and count which lights flash how many times.
Blink (a/k/a Flash) Codes – How to. | PriusChat

Another option is to use a capable scantool to check all the systems on your car for codes. Many parts stores (and some repair shops) do not have a scantool that can read all the systems on a Gen2 Prius. Here is a thread that reviews several scantool apps and devices.

Gen2 OBD2 app review | Page 2 | PriusChat

 

It's possible the only code you had was C1202 about the brake fluid level, in which case you could be confident you had resolved the problem. If you had read the code you would know.

The next person who has those lights and symptoms still ought to read their codes, though, as there are around two hundred reasons those lights come on, so the chance that it's randomly the same as your situation is not high.

 

I can’t imagine an extra quarter inch of brake fluid will cure the electronic shenanigans. Maybe some other variable changed.

if you’re changing brake pads down the road, I’d monitor the reservoir while pushing pistons back (unless you open bleeders): that extra brake fluid may overflow.

I’ve had similar behaviour on our gen 3, just brought it to dealership, immediately. It took two or three such events, eventually tracked down to a scan gauge I had constantly weighing on the OBD connector.

 

Well, there is one electronic shenanigan (specifically, the C1202 shenanigan) that flat-out means "hey, your brake fluid may be low."

That is one of the 200 or so shenanigans that can cause those warning lights to come on and the brakes to operate in a fail-safe mode, which feels noticeably different.

So if that was the code (which we don't know, as the code wasn't read), then adding the fluid may have done the trick. Otherwise, this may just be a remission, which will be followed eventually by another opportunity to read the code(s).