Five problems related to brake sensor have been reported for the 2008 Toyota Prius. The most recently reported issues are listed below.
Tl- the contact owns a 2008 Toyota Prius. The contact stated that while operating the vehicle and pressing the brake pedal an audible peeping sound had occurred and the vehicle would not immediately stop causing the braking distances would be extended. During the failure the abs, vsc, brake and battery warning lights had illuminated. The vehicle and taken to an independent mechanic who diagnosed that the brake actuator and the abs brake sensors were faulty and needed to be replaced. The vehicle was not repaired. The local dealer(unknown) was notified of the failure. The manufacture was not yet contacted. The failure mileage was 70,000. Jft.
Around 4:30pm on Saturday afternoon, we opened the car door to run some errands and were startled by a piercing noise. The dashboard was lighting up (abs & vsc) and although the car started, the dashboard remained lit and the beeping continued. When driving the car to the dealership, the brakes did not brake fully. After a $58 diagnostic test, we were told that acc pressure sensor needed to be cleared and if we returned with the same problem, we may need to replace a "brake actuator part" (cost = $2,560). Before this incident, on Saturday afternoon, we drove the car on the interstate for about 150 miles. For the last 15 minutes of our trip, we were driving through heavy rains on the interstate and on side roads. We did not experience any problems when driving the car in the rain, but are wondering whether or not the water affected the brakes.
Pulled out of parking lot, started accelerating, went to hit brakes and brakes failed. Brake pedal travel was more than normal, started pulsing brakes. Dashboard lights came on (not sure which ones). Problem also occurred in September 2011, and Toyota reset the "brake stroke sensor" charged us for this work, and recommended replacing the sensor (~500). Dealership stated this was not covered under warranty due to over three years. Even though it was a safety issue, they did not replace sensor at that time.
On 20 may 2010 at 11,966 miles every brake/stability warning light came on (including the warning for the parking/emergency brake which was not engaged), regenerative braking appeared to have failed, and hydraulic/friction brakes behaved as if abs was acting at a very slow pulse rate, approximately a 5-second cycle. For about 2 seconds during the "off" portion of this cycle the brakes were effectively inoperative, with the parking/emergency brake the only source of braking. This behavior persisted after shutting down and restarting the car. The dealer's service department reported that three errors had been logged: c1247 - stroke sensor c1300 - abs ecu malfunction c2318 - low voltage error resetting the computers cleared the warning indications and restored normal brake system behavior. At my behest, the dealer worked with Toyota engineering to identify why a low voltage would cause a computer failure which could cause substantial loss of braking ability. They kept the car for 8 days but did not appear to complete any sort of root cause analysis of the failure. On 17 December 2012 at 27,324 miles the brakes again failed with the same set of warning lights illuminated. This time, abs does not appear to be active at all. For the first 2-5 cm of brake pedal travel, in the regime where regenerative braking would be active, no braking is evident. As the pedal is further depressed, the hydraulic/friction brakes abruptly engage. Pressing harder does result in increased braking though braking is rough. No pulsation as might be expected from abs was noticed. No attempt was made to brake hard enough to lock up the brakes. The vehicle is currently at the dealer.
Even when new, only when braking on a bumpy surface, my 2008 Toyota Prius will reduce braking power all by itself, when I need them the most. When I press into the brake pedal, it will brake again, but by this time I will have lost 1 second of braking time. Recently on Jan 20th, I almost hit the person in front of me when I had to panic-brake, and the road became bumpy as I was braking. By pressing the brake harder after 1 second lost, I barely stopped in time. I never brought this to the dealer's attention, until two weeks ago, because I know this car has hyper-active wheel-slip sensors, and I just thought it was part of that design flaw. That problem comes up whenever I try to accelerate hard and make a right turn. Even on dry pavement (and no wheel slip) the engine cuts out for about 3 seconds and the traction control light comes on. When it was new, the dealer said that's just the way it's designed. But that's not what I'm complaining about. That's just why I didn't report it until now. Back to the brakes, two weeks ago, when I heard the 2010 Prius has a software update to fix this problem, I thought they might be able to fix mine also. But when I went to the dealer, they said they couldn't do anything with it unless there was a recall, and there isn't for the 2008. They gave me the number to report it to Toyota. I did that on 02/10/2010. Then when I heard the Toyota president (2 days ago) say that earlier Prius' don't have the problem, I thought I should report it to you also. Ps. . . I am an analyst by trade, I am highly mechanically inclined, and have even done my own brake jobs. I know how brake systems work and have had many cars with abs and traction control systems. This is the first car I have had that does this on a bumpy road surface.