2015 Toyota Prius Brakes Problems

Code DTC C1391 - Abnormal leak of accumulator pressure. Internal failure of the brake booster pump assembly, preventing the system from maintaining proper hydraulic pressure. This means the brakes don't work, putting the driver's and passengers' lives at risk. This DTC C1391 code and problem were reproduced and confirmed by an independent service center who specializes in 3rd generation priuses. There were warning lights that lit up when the brakes failed - the ABS, traction control, and brake light all lit up but only after the brakes had stopped working. This is a known manufacturer defect but toyota won't pay to fix it because they put a 10 year limit on first driven date or 150,000 miles. This prius only has 100k miles but toyota still won't stand behind their product even though they have admitted it was a manufacturing defect and they sold a defective product.

NHTSA ID

11756229

Incident

Aug 6, 2026

The vehicle experienced a failure in the braking system involving the brake booster/brake actuator assembly. The vehicle displayed diagnostic trouble code C1391, which is associated with a malfunction of the brake booster pump/accumulator system on this model. The failed component is available for inspection upon request. The failure created a safety concern because the braking system warning lights illuminated and the vehicle’s brake assist system may not function properly. A malfunction of the brake actuator/booster system could increase stopping distance, reduce braking performance, and create a potential risk of a crash, especially during emergency braking situations. The problem has been confirmed through diagnosis showing the C1391 trouble code. The issue has been identified as a brake system malfunction requiring repair of the brake booster/actuator assembly. The vehicle has been inspected/diagnosed by a service professional. The vehicle has not been inspected by police or insurance representatives. Toyota/dealer inspection information is available if requested. I contacted Toyota regarding the issue, but they declined assistance because the extended warranty coverage expired approximately 7 months prior to the failure. Before the failure, the vehicle operated normally. The first symptoms occurred when multiple warning lights appeared while driving, including the ABS warning light, brake warning light, parking brake warning light (even though the parking brake was not engaged), and the traction control/slippery road warning light. These warning lights appeared suddenly, indicating a problem with the braking system.

NHTSA ID

11746503

Incident

Jun 23, 2026

The contact owns a 2015 Toyota Prius. The contact stated that while driving at 45 MPH, the brake warning lights illuminated. The brakes were inoperable and entered manual mode. The contact stated that the brake warning lights were red and yellow. The vehicle was taken to Brake Masters, where it was diagnosed with brake actuator failure. The local dealer was contacted but did not provide assistance. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 121,000.

NHTSA ID

11743224

Incident

Jun 6, 2026

Mileage

121,000 mi

The incident involved having to press extremely hard on the brake pedal to stop the car, while it was uphill in the middle of the road. The car started going backward and was throwing ABS, Master Warning Light, Brake System Warning Light and Warning Buzzer, Brake System Warning Light, and SLIP Indicator signals. This was a highly distraughtful situation on the road. Diagnostics showed C1391 Diagnostic Trouble Code on the 2015 Toyota Prius: brake booster and brake booster pump problem. When pressing the brake pedal there is a high pitched metal scraping noise. Toyota coverage program is only applicable for 10 years from the date of first use or 150,000 miles, whichever occurs first. Many cars run well for over 10 years with good care, so the 10 year cap barely covers anything. This is highly unfair and borderline scamming for an issue so severe, which can cause big accidents on the road. In all honesty, this is a life or death situation when it comes to not being able to properly brake while driving. This should be a full recall!!

NHTSA ID

11742921

Incident

Mar 28, 2026

The brake pump and actuator on my 2015 prius has been faulty and the repair was apparently covered under the customer support program but it expired in December. I had no knowledge of it and when I took my car in to a toyota dealership, no one told me about about the profram but told me that they needed to be replaced. I did not get the repair because of the hefty cost and I missed the deadline. My safety and the safety of other drivers were put at risk for not allowing me to be notified by it and my car being at risk for my brakes failing at any time. Their were absolutely no warning lights on my vehicle as well.

NHTSA ID

11741829

Incident

Dec 17, 2025

Code C1391 200k miles All the warning signs for brake booster issue came up. The cost is too high and I just missed the Customer Support Program timelines because the code came up late. This needs to be a RECALL, based on how many people experience this issue consistently.

NHTSA ID

11740166

Incident

May 6, 2026

I was driving my 2015 prius for years and occasionally the brake, abs and traction light would come on this is a sign of a failing Brake actuator and booster. Toyota and the Ntsb ordered the following warranty enhancement https://static.nhtsa.gov/odi/tsbs/2020/MC-10181800-9999.pdf My Brake Booster had been exhibiting signs of failing for years and I tried to get a toyota dealership to replace and repair the parts under the warranty extension but I was told I had to wait until I had perminent dash lights and trouble codes. So I had to wait till the booster completely failed. By that time my car had exited the extended warranty perimeters and I am told it is no longer eligible.... even though the components are faulty from the factory and exhibited signs of failure many years prior. I was told to wait until the compenent failed by multiple dealers. My car was in motion and the brake boosters failed, fortunatly it did not cause an accident but this is a serious safety issue. Toyota should have done a compleat recall of the brake actuator and booster pump, rather than have drivers use known faulty components until failure. Toyota corporate has refused to help in the repair of the vehicle despite it showing failure for years.

NHTSA ID

11740085

Incident

May 23, 2026

Toyota Prius has a known problem with the brake actuator and booster. A notice was sent out in 2019 under the Customer Support Program Expansion with repairs up to 10 years or 150k miles. This is a safety issue and should be covered under a recall with NO TIME OR MILEAGE LIMITS since these problems are not showing up until after 10 years if the car has low mileage, as in our case. We just passed the 10 year mark, but only has 114k miles. No mention of repairs needed were made during regular maintenance visits with Toyota. Additionally, preventative repairs were not offered if the vehicle did not seem to be experiencing problems at that time. The brakes are spongy and unresponsive. The ABS light , traction warning lights, and parking brake lights are staying on.

NHTSA ID

11736895

Incident

May 4, 2026

ABS braking system suddenly not working. ABS, BRAKE, and traction control lights all turned on.

NHTSA ID

11736350

Incident

May 5, 2026

On 4/16/26, while driving my 2015 Toyota Prius (approximately 87,000 miles) on the freeway, I applied the brakes while transitioning from the [XXX] onto the [XXX] . As I veered right on the curved onramp, the brakes failed to engage properly, causing the vehicle to spin out of control and collide with the side railing. There were fortunately no nearby vehicles on the 2-lane onramp at the time. Under slightly different circumstances, this incident could easily have resulted in serious injury or death to myself and/or others. No airbags deployed. Although I was physically unharmed, I was extremely shaken by the incident. Immediately after the collision, the brake warning light, ABS warning light, and another warning indicator illuminated on the dashboard. Prior to the incident, I had not experienced braking problems severe enough to suggest imminent failure. On 4/17/26, I brought the vehicle to Toyota of Cerritos for diagnostic evaluation. I was informed that the brake booster was the issue and that the vehicle was unsafe to drive. The vehicle was towed to a collision repair center affiliated with my insurance company. After repairing the external collision damage, the collision center informed me that the brake booster malfunction that caused the incident could not be repaired there and would require dealership service. External repair alone: $3706, in addition to increased automobile insurance premiums expected over the next 3 years. I also contacted Toyota Motor Corporation regarding Customer Support Program coverage related to brake booster issues and was informed that the program expired in 2025 and no assistance would be provided. I am submitting this report because this brake booster malfunction created a serious and unexpected safety hazard resulting in loss of vehicle control on a freeway interchange. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11736160

Incident

Apr 16, 2026

My brake actuator and brake booster are failing. All of my dashboard lights have come on (brake, ABS, Traction Control, brake system warning light). Unfortunately, I am over 10 years and Toyota is saying that I need to pay out of pocket for the repairs. This is a known problem and should be covered. I was unaware of the known issue and my car didn't start having problems until after the 10 year mark. I am under 150,000 miles.

NHTSA ID

11725978

Incident

Mar 20, 2026

Brake Booster and ABS, Brake Master Cylinder went out in car without any lights or warning while driving the vehicle at a moderate speed on Freeway. I was able to avoid an accident and take the car to a repair shop in which at 119K miles and just at 10.5 yrs old the entire brake system had to be replaced/repaired.

NHTSA ID

11725935

Incident

Mar 7, 2026

In June 2025, while driving on the highway, the vehicle suddenly displayed multiple brake warning lights and warning messages, including the red brake warning light, ABS light, brake system warning light, and traction/slip indicator. At the same time, the brake pedal became stiff and braking effort increased suddenly, creating a near-crash situation because the vehicle did not slow normally. Before that incident, the vehicle had already been making abnormal brake-related noises, including a humming/pumping noise when the brake pedal was applied, and there were intermittent episodes where braking felt abnormal. In June 2025, the vehicle was taken to a Toyota dealership during Toyota’s brake booster support program period. The dealership documented customer complaints of “humming noise in cabin when holding foot on the brakes,” a request to “scan for codes for ZJB enhancement,” and that the “vehicle hard to accelerate and brakes got stiff,” but stated that no qualifying ABS codes were present at that time. In March 2026, the same condition returned and worsened. The vehicle again displayed the red brake warning light, ABS light, brake system warning light, and traction/slip light, and braking performance was reduced. An OBD scan of the ABS control unit showed code C1391, which is associated with brake booster / ABS actuator failure. The Toyota dealership has now diagnosed the vehicle with ABS actuator and brake booster failure and quoted repair. This is a serious safety issue because braking became more difficult while driving, including on the highway, with sudden warning lights and degraded stopping ability. The failed components are available for inspection. The problem has now been confirmed by a Toyota dealership. The issue was reported to a Toyota dealership during the prior support-program period but was not confirmed then.

NHTSA ID

11725874

Incident

Jun 15, 2025

TOYOTA PRIUS ABS BRAKE PUMP ACTUATOR BOOSTER FAILING Making hissing noises and warning icon at only 10 years 9 month, 85,000 miles. Toyota extended warranty is NOT covering.

NHTSA ID

11724157

Incident

Mar 13, 2026

On Feb. 19, 2026, I went to an auto repair store to change oil. I was told that I need to have rear brake pad and rotor replacement service because my car does not have it. The mechanic showed me and said that I only have the front brake work and it can cause safety issue.

NHTSA ID

11719651

Incident

Feb 19, 2026

Inferior brake system on 2015 Prius master brake cylinder and vacuum booster. Extended warranty issues identified by Toyota for 10 years or 150, 000 miles. I bought my Prius used in 2021 with 92,000 miles at age [XXX] old intending it to last as long as I did. I am now [XXX] old and essentially totally independent. The above mentioned parts were identified as not functioning properly on 2/3/2026 (mileage 139, 106). On 2/6/26, I took it to Goettle Toyota, Ocala FL (mileage. 139,160) knowing there was an extended warranty program available that was admitting the parts were defective but not worthy of recall. I was advised the warranty for my vehicle expired 10/26/2025 (3 months and 8 days prior) and was now invalid. Brake replacement cost is $3675.00 + tax🥴. I was provided warranty information and instructed to call Toyota. I called, spoke with Brook and was advised the warranty was invalid due to date even though the car has less than the 150, 000 mile covered and nothing could be done. I was never notified of this issue so I could monitor for problems before the expiration. Average life for these items on a Prius is 250,000 miles, not 139, 000. I am on limited, fixed income and cannot afford this unnecessary repair. I am already gladly driving a 10 year old car to be independent. Loss of transportation changes my entire lifestyle. I cannot afford another car (if I could, I would be fixing this one). I would be reliant FOR THE REST OF MY LIFE, on others for all needs outside of my home. I live in a very rural area. I feel since I was NEVER notified of any issues and the car is LOW mileage and there should be another 100,000 miles on this car (I have driven it less than 50,000 miles in 5 years) that Toyota should honor the extended warranty based on the proximity of the malfunction to the ending of the warranty period and the LOW MILEAGE of the vehicle. This amount of money is NOTHING to Toyota but it is LIFE CHANGING to this, up until now, independent woma INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFOR

NHTSA ID

11719106

Incident

Feb 3, 2026

The brake booster suddenly fails at 54k mile. Brake responds slower and need to push the brake pedal all the way It seems a lot of 2010-2015 Prius are facing this problem ABS light, skid light, and brake light was on when it happened, first appeared on Feb 6, 2026 Have to replace brake boost for ~$1500

NHTSA ID

11716793

Incident

Feb 6, 2026

The contact owns a 2015 Toyota Prius. The contact stated that while driving at an undisclosed speed, the ABS and the traction control warning lights illuminated. The vehicle was taken to an independent mechanic, where it was diagnosed with a leak in the brake fluid hose. The contact was unsure what repair was performed, but the vehicle was repaired. The contact stated that the failure reoccurred with an abnormal sound. The vehicle was taken back to the independent mechanic, and the contact was informed that the vehicle needed to be taken to the dealer for a complete diagnostic test. The vehicle was taken to the dealer, where it was diagnosed with brake booster failure. The contact was informed that the brake booster needed to be replaced. The vehicle was not repaired. The contact was notified of Customer Support Campaign: ZJB; however, the contact was informed that the repair was not covered under the Customer Support Program because of the 10-year 100,000-mile limitation. The manufacturer was made aware of the failure, and a case was filed. In addition, the contact stated that the Customer Support Program: ZJB, was mailed out to customers 10 years ago. The contact stated that the information was never received. The failure mileage was approximately 114,000.

NHTSA ID

11716168

Incident

Feb 6, 2025

Mileage

114,000 mi

ABS break actuator and abs pump failed while driving losing loss of breaking. Toyota is aware of this problem but refuse to fix this notorious and dangerous problem they have with multiple model years. I was not informed of the limited service campaign. This should be recalled as a safety to the public.

NHTSA ID

11714486

Incident

Jun 5, 2025

Defected brake booster hard brake suddenly car less than 100 000 miles many vehicles with the problem

NHTSA ID

11711545

Incident

Jan 6, 2026

I purchased a vehicle a year ago whenever my vehicle was still under the tenure and the 10 year and it’s still under 150,000 mile range. The vehicle was purchased strictly from the Toyota dealership in Lakeland, Florida, and shortly thereafter my brakes completely went out and the booster actuator assembly looking it up by further realize that is a very common issue and that there is so much that there’s class action lawsuits and also instead of it having a recall, it has a customer support to replace parts. My car is very dangerous and doesn’t have any brakes and it’s still very new from the dealership. What it’s very interesting is that it’s not throwing any codes at all, though it beeps the entire time that I’m in the vehicle with the ABS light on and I know that it’s that problem why is it not showing any codes I think that for sure, the dealership would’ve had to done something to prevent that in order to sell the car unsafely

NHTSA ID

11711319

Incident

Jan 1, 2026

While driving, my brakes became mushy and ineffective. Brake warning lights came on, also. It was very scary driving in rush hour traffic with little to no brakes. There was no reliability. Just keeping as much as possible space between cars, using Hazard lights &prayer.

NHTSA ID

11710539

Incident

Dec 16, 2025

The ABS failed while driving on the highway. There was no accident, but it was substantially harder to brake when needed.

NHTSA ID

11706188

Incident

Dec 19, 2025

This vehicle has 95k miles, now the vehicle has a brake problem which can cause deadly problems. The parts that have gone bad on this car are defective parts that toyota knows about. The warranty they extended for this ended in 02/2015. They had 150k miles or 10 years limit on that warranty. We are well under the mileage and 10 months over according to toyota. Can’t believe they will dismiss something this delicate and dangerous. The parts are not cheap and it’s something we can’t afford to fix right now. I can’t believe Toyota will just wash their hands on something this important in a vehicle. This is a know defective part! They should have some sort of responsibility and resolution. I called and was told they cant do anything. Even a part offer so we can fix nothing. Please review this and hopefully you can help.

NHTSA ID

11705297

Incident

Dec 13, 2025

The vehicle has 95k miles on it and both brake actuator assembly and booster pump have gone bad. This is a defective issue, I called toyota and was told too bad since the program that fixed this ended 02/25. The car met the mileage requirement, but being 10 months out of the date gives toyota the right to wash their hands on a defective part. The part is over $1500 just in parts to replace! This is wrong on their part. Not one option offered.

NHTSA ID

11705276

Incident

Dec 13, 2025