Brakes squeak consistently but only after brakes have been used.

[Tommy André]

My 2015 Toyota Auris keeps squeaking when I drive under 30 km/h but only after a little time and brakes have been used. I saw something about brake booster not letting brakes go all the way back but that might be wrong. Thoughts?

[TonyHSD]

Hi, 

brake booster has nothing to do with the brake issues that you might have but rust and dirt might do. If the brakes hasn’t been serviced in the last 2-3 years most likely they need some attention, nothing too complicated. , just dismantling, cleaning, lubricating, might also need new pads and discs and a fresh brake fluid. 

[AisinW]

Check and clean all the mating surface where the brake pad slides including sliding pins.  If you still have problems, time to check with OBD2 Sscanner if there is any engine code.  Some 3rd gen prius got free brake booster campaign in USA until last summer.