When I start my prius 2007, sometimes the ABS, VSC, (!) and the red parking brake lights come ON (even when parking brake is not engaged) simultaneously along with the sound of a warning buzzer. This condition persists for an unspecified amount of time (sometimes for 3-5 seconds, sometimes for 10, 15 or may be 40-60 seconds). During this condition, the car otherwise functions well except that the brakes don't work. A day before, when I started the car after having parked it for about an hour and a half to have dinner, the ABS, VSC, (!) and the red parking lights came on along with the warning buzzer and did not go off even after waiting for a few minutes. Then when I put the car in D and started moving, the brakes didn't work as expected. I started idling at a speed of 15-30 km/h but in order to stop the car, full pressure needed to be applied on the brake paddle and even then the car would stop very slowly after covering quit a distance (for example, at 15 km/h it would stop after 20-30 meters approximately when brake paddle was fully pressed). This condition persisted for quite some time and the warning lights and the warning buzzer remained ON all the time. I traveled this way from F-7 to G-11. Then the warning lights and the buzzer went OFF suddenly by itself and the brakes and everything else worked perfectly well. It is still working well, except when starting the car the next morning the same condition persisted for a few seconds and then it was fine.
I searched the web for the problem and found that a lot of people using prius have the same problem, some suggest replacing the stop light/brake light switch, others say that it is because of the 12v battery going old. Toyota capital in isb scanned it and did some tweaking but said that a 'pressure accumulator' may need replacement if the problem persists. This condition has not occured after getting it checked from Toyota except that the ABS, VSC, (!) and red parking lights stay on for 3-5 seconds alongwith the warning buzzer upon starting the car after parking it.
Any help would be really appreciated.