Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2009 Toyota Prius owners, lightly cleaned up (personal details are redacted by NHTSA).
Upon starting the vehicle it makes a high-pitched beep, followed by a buzzing sound that repeats every five to eight seconds. The dashboard displays the tps, ABS, vsc, and brake lights. When putting the vehicle in drive, the high-pitch sound returns for one to two minutes. During that time the brake pedal becomes impossible to depress. If the engaged, the vehicle does not stop until the brake pressure returns. Once the sound stops, the brake pressure returns to normal. Diagnosis from Toyota shows: code c1256 = accumulator low pressure. Code c1391 abnormal leak of accumulator pressure. Estimate for repairs = $2,811.72. At present the vehicle is unsafe to operate as Toyota advised, in the vehicle's current condition the brake system could fail at any time.
Traveling 101 north toward ventura, on the top of the down hill grade just south of the camirillo springs exit. All lights on panel came on. Estimate 65 MPH, applied brake to slow with traffic flow. No brakes,no warning.semi tracker trailers also slowing. Took exit bottom of hill with flashes on, went thru stop sign as my speed at approx 45-48mph. Went thru second stop sign made sharp left pulled emergency brake on... This is a garage car serviced by dealer only, 3rd time for electrical problem! Never while driving.... This was near fatal! This was an electrical problem of the manufacture, never repaired correctly! Have 3 copies of repairs for the electrical starting 6 months after purchase car...help.
Every day I encounter a large pot hole on my way to work. It is about 20 feet from a stop sign, so at this point I am already driving slow and braking. However, when the one wheel dips into the hole, the yellow traction system light comes on, and I feel what could be a slight loss in braking, as if the car is coasting for a split second (versus braking/slowing) or perhaps accelerating forward. The car/system recovers as soon as all wheels pass the pothole. Not having had a traction control system prior to this car, I didn't know what was normal so I didn't pursue it, but I know I don't like how it feels! This has been happening every time I drive over that pothole since I bought the car. Luckily they just paved the hole last month finally. Otherwise I try to avoid rough roads as a matter of course. …
It is a recurring incident/problem with my 2009 Toyota Prius. Braking at the same time one is going over a bump in the road or during intermittent slippery conditions. When braking at the same time the car is going over a moderately abrupt bump or parkinglot driveway entrance the anti-lock braking engages but there appears to be delay - possibly in connection with the switching from the regenerative brake mechanism - causing the sensation that the brakes have failed for about 1 second or 2 - quite a disconcerting feeling and concern that is potentially dangerous if the same road conditions were present during a panic stop. During intermittent slippery conditions - e.g. Snow over the road, partially plowed snow or icy conditions - the anti-lock braking/traction control is over-active, cutting power abruptly to one wheel then the other causing a whipping action from side-to-side. …
As I was driving my 2009 Toyota Prius on the service road of I-30 in dallas around 25 MPH after previously taking off from a red light, my vehicle's warning lights all turned on and started to beep and I could not brake or really steer. My vehicle...I almost hit the vehicle in front of me. Somehow I was able to turn right into a parking lot and somehow press on the brakes strong in enough to make the car stop. I feared for safety and the safety others as well. It was a very scary situation to be in a car that was not responding when you are trying to break and there's nothing you can do about it. Once I was in the parking lot, I turned the vehicle on and off and the lights were still on and beeping, did it again and it stopped. …
On a daily basis, my 2009 Toyota Prius loses control, skids, (the traction light goes on), fishtails and has brake failures on ice and snow. When I hit potholes or big bumps, the car accelerates and I have to quickly brake. The northbrook Toyota service manager drove it today. The car lost control, skidded, the traction light went on, it fishtailed, and the brakes failed on the ice and snow. His comment was "that's the way the car is. It doesn't drive well on ice and snow". We couldn't find a good pothole for the car to demonstrate the acceleration today. I was told by an automechanic that works on our other cars that the 2009 and 2010 Prius have problems with their brakes. Presently there is no recall for the 2009 Prius. I am afraid I am going to kill someone at an intersection when I can't stop. …
Applying light to moderate pressure on the braking pedal of my 2009 Prius while simultaneously going over a pothole at low to moderate speed (such as in traffic) causes the braking system to release and the car will fail to stop. Removing pressure from the pedal and reapplying pressure to the brake pedal usually regains braking function but causes a few seconds of lost braking. This is easily repeatable and frequently occurs in the same spots on a daily commute for the past year I have owned this car. On two occasions soon after purchasing the car in October 2008 I was still unfamiliar with this braking "quirk" and rear ended two separate cars on different occasions. There was minor damage to both bumpers of the vehicles. Both occasions were in heavy traffic traveling under 10 miles per hour, attempting to brake with unwittingly hitting a pothole at the same moment.
2009 Toyota Prius. Strange behavior of antilock brakes/traction control system when hitting a single pothole or small patch of ice on otherwise clear road surface. Vehicle significantly dampens brake response and does not recognize that the tires are now on a good contact surface and continues to be in tc mode for excessive time period. Only way to assure you will stop within reasonable distance is to lift up on brake pedal and redepress (now out of tc mode car will stop quickly). This problem presents itself regularly when road conditions are right. The problem is the most noticeable at moderately low speeds I would estimate 5-25 MPH but likely occurs at higher speeds which is less noticeable. It seems to be a factor of distance or the fact that the car does not realize the wheel is getting traction again.
In addition to the traction control, ABS, gas pedal/floor mat problems with the Toyota Prius there is also a safety issue with the power button. In an emergency situation, like the door coming open, throttle getting stuck, etc. You can't power off the vehicle quickly. You must hold the power button for some amount of time before the car will shut off. Unlike the Toyota camry example where they suggested turning off the ignition, you can't do that on the Prius. You also can't remove the key/fob to turn the vehicle off or power it off. There is also an extreme under steer problem with the vehicle which is a safety concern. In wet conditions it is exacerbated. It can be observed on clover leaf overpasses and general cornering.
2009 Toyota Prius: when driving over pot-holes, bumps, or uneven patches of road at all different speeds, the car's "traction light" will flash and the car will momentarily surge forward. It seems at this time that the brakes also temporarily lose power. This happens several times a week. This worries me as I feel this could lead to car accidents or put pedestrians in danger. Spoke with many other Prius owners and they report the same problem. Contacted the dealership where I bought the car and the service manager told me this was a "normal function" of the ABS. I still feel this is a safety issue that is not being properly addressed. I've driven many other cars with ABS and none of them behaved this erratically.
Traction Control complaints in other Prius years
Frequently asked questions
How common are traction control problems on the 2009 Toyota Prius?
NHTSA has 27 complaints about the stability & traction control of the 2009 Toyota Prius, 5% of the model year's 502 complaints.
Is there a recall for 2009 Toyota Prius traction control problems?
No. NHTSA lists no stability & traction control recall for the 2009 Toyota Prius, though it has 6 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2009 Toyota Prius traction control problems start?
Half of the complaints with a recorded mileage happened before about 16,000 miles, and 71% before 25,000 miles.
Is it dangerous?
Owners linked 1 crash, 0 fires and 0 injuries to stability & traction control problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.