Three problems related to brake abs warning light have been reported for the 2013 Toyota Prius. The most recently reported issues are listed below.
Vehicle brake actuator continuously pumping and running even when vehicle is off or stopped, abs lights can light up under moderate braking on dry roads. Earlier generations of the Prius had similar issues and Toyota added an extended warranty to cover a rather expensive repair that could compromise the safety of the vehicle. There is a well known issue with this braking system when reading further on Toyota Prius forums.
Own a 2013 Prius v. Noticed about 5 times over past 2 years-when car starts after sitting overnight (12 hours) and put into gear, car will roll back while foot is depressed on brake. After a few feet of rolling and pumping brakes, car will stop. No injuries or damage sustained as car was in flat carport. Over past 6 months, braking while at low speeds (less than 5 mph), produced a rhythmic jerking type of stop. Dealership diagnosed problem as needing replacement of brake booster pump and master booster assembly. Drove car without repair for 1. 5 more months when abs warning lights came on while on the freeway. Stopping distance greatly increased and need to press the brake down hard was a significant difference. Wrote to Toyota headquarters as well as local servco which is the main Toyota/Lexus/Subaru dealer in hawaii. They declined to my request to repair the defect at no charge stating car is not covered under the zjb customer support program that Toyota already has in place for 2010-2015 Prius and Prius plug in (but not the Prius v). Dealer states the zjb program is a "courtesy" for those covered vehicles. This is a defective part that Toyota and servco knowingly sold to the consumer-it is a consumer safety issue.
Experienced what appears to be a common malfunction of the abs system. Went over a regular road bump on a city street, nothing drastic, while braking. Immediately after, the traction control, brake, and abs lights came on solid. There was still some braking available, but it required much more force and pedal travel to achieve the same level of braking as before. This could be very dangerous if someone then needed to stop suddenly. I was able to drive home. Found some forums on line about this problem, which appears to be widespread. Using a paperclip, I was able to �reset� the system, clearing the warning lights and reestablishing abs and regenerative braking. . . But only for a short while. Later in the day, the same malfunction occurred, with the same warning lights appearing, loss of abs and regen braking.