4 warning lights came on

Accumulator?

 

He means your brake booster hydraulic accumulator. It has a pump to build hydraulic pressure for your drive by wire brakes. An accumulator stores hydraulic pressure so its immediately ready. A leaky accumulator or a bad pump or a bad master cylinder will throw codes and is dangerous.

You get the alarms before it fails completely. Unfortunately, it is a common problem in older Prius vehicles.

 

Sorry, no - I mean the brake accumulator that stores pressure to operate the brakes.

 

The brake system on the Prius is pretty complicated compared to most vehicles, so unfortunately, you're exceeding my pay grade with that last question. It's possible that the accumulator is part of the actuator, or an ancillary component.

 

LOL. Well at least you're willing to say that. Yes the car is pretty complicated once it starts developing problems and warning lights are all lit up.

 

Just read the trouble codes and find out why the lights came on. The codes can be posted here. Smile at all of the nice guesses about what your problem is that are posted before we know the codes.

If you don't have access to a scan tool to get the full story, you can get the two-digit blink codes with no special equipment, as a bunch of threads around here describe.

 

What is the measured voltage?

 

Not a bad plan. You also have easy access to two-digit blink codes without any special tool, in case you want to know something before the trip to the dealership.

 

No, he means to find abbreviated blink codes using the Blink Light method.

See this post for how to do that: Prius Gen2 Blinking Lamp Example

Read through that first post so you get an idea of what to look for in the video. There is no soundtrack explaining what is happening. Also, choose a wire with nice clean, firm, and reasonably flat ends so you don't cause any damage to the terminals at pos 4 and 13.

OBDII Position 4 and 13:

Post back here with which lights blinked what codes if you want help.