2012 Toyota Prius C

While driving 65 mph on the expressway on January 12th, 2026 under cruise control, I tapped my brakes to slow down. My brake warning light came on, along with the ABS warning light, and the anti-swerve warning light. Cruise control no longer worked, and my brakes were noticeably hard to apply. I immediately had the vehicle computer checked and the issue is a leaking brake booster component, a faulty part known by Toyota to fail prematurely with this and other Prius models. No recall was issued however. The car is now unsafe to drive until a ~$4000 repair is done, according to my service representative.

I own a 2012 Toyota Prius C with approximately 156,578 miles. The vehicle has been diagnosed with C1391 – Abnormal Leak in Accumulator, which causes the brake actuator to lose hydraulic pressure. This results in frequent buzzing from the actuator pump, illuminated warning lights (BRAKE, ABS, Traction Control), and loss of ABS and stability control. The condition increases stopping distance and creates a serious safety hazard. Toyota previously acknowledged this exact defect under Customer Support Program CSP 21TE01, which covered brake booster and pump assemblies for certain Prius and Prius C models when codes such as C1391 were present. However, the program expired on November 30, 2022, and my vehicle is just over the 150,000-mile coverage limit. Despite this, my Prius exhibits the same defect that Toyota has already recognized as a safety-related issue. Toyota Carlsbad confirmed the diagnosis and quoted $3,399.55 plus tax for repair, with a reduced courtesy estimate of $2,817.86 plus tax, but declined goodwill assistance since CSP 21TE01 expired. Given the widespread reports of brake actuator failures in Prius models, I believe this represents a systemic safety issue that warrants NHTSA investigation and potential recall/extended coverage.

Brake Actuator and ABS Accumalator failed. It is a common failure reported by multiple owners on these cars. I was on the high way going 70 when it failed and lost any brake boost I had putting me in a very dangerous situation where I narrowly avoided an accident. Upon scanning the car's codes I got code C1391 which I looked up and saw a bunch of other people who were also struggling with this issue.

I am writing to express a complaint regarding the issues I have experienced with the brake system of my Toyota Prius C, 2012 model. For the past several months, I have noticed that the brakes exhibit strange noises, soft pedal sensation, reduced braking efficiency, were driving and the ABS, traction, brake, and that other light turned on and the brakes became slow these issues have been observed on multiple occasions and pose a safety risk to myself, other drivers, and pedestrians. I have taken the vehicle for inspection, but the problems persist or have not been definitively resolved. I believe these faults may be related to defects in the braking system, and therefore I request a thorough inspection and necessary repairs at no cost, considering that the manufacturer could be responsible for manufacturing defects.

The brakes on this Prius started to make weird noises. Because it is a hybrid, I wasn't sure if it was normal. After searching online, it is a known issue. The car has just under 76,000 miles on it. It might be worth $7000 on a good day. Toyota wants to replace two brake parts, numbered 47050-52020 and 04006-74152 to a tune of $2700. According to a Toyota bulletin, this job should take 2.3 hours. For that amount of work, my local Toyota shop wants almost $2000 in labor. My car was seen by the local shop (being on an island, it is literally the only Toyota shop that this car can be seen) when the "customer support program" 21TE01 was in place and they did nothing. Now, the time window has disappeared, even though we only have half of the maximum number of miles to get the repair. Toyota should be ashamed of themselves.

I was driving down the interstate with my cruise control on when all of a sudden the cruise control disabled and warning lights came up on my dash board. It still drove fine for several weeks. On Friday December 6th, I was going down the road and had to press the brake slightly for a car turning. When I pressed the brake, the car went into a spin. It spun a couple of rotations. Luckily I was on a wide part of the highway and no oncoming cars were approaching. Toyota had a recall for the same code and parts for the 2010 Prius but did not include the 2012 Prius. They just had an alert which I did not receive because the notice went to the former owner. However, I did take my car in for oil change and diagnostic but they did not tell me that there had been a problem with these parts. They want almost $4,000 to repair it. Why would they not include ALL vehicles with this same part. If it fail on one, it will fail on another. I think Toyota should make them all good. Please make them issue a recall for all of these parts. I took my car to a mechanic but because of special tools needed, you have to take your car to the dealership for repairs. When I called the dealership, I was told I needed a break booster pump and a brake master cylinder for a total of $3, which is ridiculous on a $7,000 car.

While my daughter was driving brake pedal faded and rear brakes locked up causing her to lose initial control of car . Steering felt tight . Many warning lights , check hybrid system , brake lights , steering warning lights , along with abs lights came on . Took car to Toyota dealer to diagnose it needs brake booster and master cylinder module . Service consultant said known issue with TSB but it had expired . Many , many complaints of this same incident of Toyota and Prius forums .

Code C1391 shows in which the accumulator and the brake booster assembly need to be changed. This is a known defect and was covered through an ‘extended warranty’ due to a lawsuit. Since it results in less than optimal braking, and can result in crashes since function disappears suddenly, it should have warranted a recall. This issue is also known to happen in multiple Toyota hybrid vehicles.