Warning lights come on and off

It's never a good idea to buy a car that needs a jump start. The stored codes will not be available if the battery is dead, potentially hiding serious problems with an electric/hybrid vehicle.

I would go have the battery tested and see if it needs replacement. Fully charge/replace the battery if needed. Then have the car looked over to see what codes return after the battery is in good health

 

obtain an obd 2 scanner! they are cheap and really helpful with diagnosing the lights/codes

 

I would assume that one of the brake system ecu's (computer) is detecting an intermittent fault and is warning you about it. Might want to first check all fluids underhood- engine oil, coolant in the radiator and inverter tank, as well as brake fluid level.

If warning lights and the beeper come on then there should be diagnostic trouble codes in one of the computers in the car. You should have a shop check all systems for codes. Thing is most OBD2 scantools are not capable of "talking" to all of the 14-16 systems on a Gen2 Prius. So you might have to look for a place that can do it.

Another possibility is to (carefully) jumper two specific pins of the diagnostic port under the dash with a short length of wire (with the ends stripped). This will signal some of the ecu's to flash their warning lights in a sequence. If you note which light flashes how many times (helps to take a video), then you can figure out what system has what codes. Use the search feature to look for "flash codes" in the Gen2 forums to locate the procedure.

From there you can look for what those codes mean in the service manual- if you use google you should be able to find a digital manual (on google drive?)

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