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…
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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 ODI #11756229
Mileage unknown · May 26, 2026
Forward Collision AvoidanceService Brakes
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 ODI #11740166
Mileage unknown · Mar 20, 2026
Forward Collision AvoidanceService Brakes
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…
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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 ODI #11725874
Mileage unknown · Jan 12, 2026
Forward Collision AvoidanceService Brakes
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 ODI #11710539
Mileage unknown · Dec 19, 2025
Forward Collision AvoidanceService Brakes
The ABS failed while driving on the highway. There was no accident, but it was substantially harder to brake when needed.
NHTSA ODI #11706188
Mileage unknown · Jun 21, 2025
Forward Collision AvoidanceService Brakes
Failure of brake pump and brake cylinder assembly system, resulting in reduced braking ability and stiff brake pedal. Per Toyota's diagnostic: trouble code C1391 is present, abnormal leak in accumulator, replaced brake ABS actuator assembly, along with brake master cylinder, and bleed the brake hydraulic system. No warning lamps…
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Failure of brake pump and brake cylinder assembly system, resulting in reduced braking ability and stiff brake pedal. Per Toyota's diagnostic: trouble code C1391 is present, abnormal leak in accumulator, replaced brake ABS actuator assembly, along with brake master cylinder, and bleed the brake hydraulic system. No warning lamps or safety indicators prior to failure. Upon failure (while on freeway going 50+ MPH) the ABS, Brake, and traction control warning lamps illuminated. The failure resulted in no accident or injury, however it did occur while on the freeway going freeway speeds, and resulted in difficulty in braking, which was dangerous. Took Prius into Toyota dealer for diagnostic and repair, was told that part was known to fail in this model of Prius, and had a manufacturer designated extended warranty for 10 years or 150,000 miles. However, despite prius being under 150,000 miles, it passed ten years since purchase in march 2025, meaning I had to pay in full for the repair ($3,631.96). The car gave no indication of needing the repair until the day of the failure, which was on June 18th 2025. If the vehicle had given some prior indication of brake pump system failure or fault I would have had it repaired prior to the warranty expiration, but it did not, leaving me to pay out of pocket for a failed part that Toyota is at fault for making prone to failure.
Toyota Motor Engineering & Manufacturing (Toyota) is recalling certain 2013-2015 Prius and 2014-2017 Prius V vehicles not included in recall 18V-684. Excessive voltage in the Intelligent Power Module (IPM) within the inverter may cause the hybrid system to shut down, causing the vehicle to stall while being driven.
Consequence & remedy
Consequence: An unexpected hybrid power system shut down may increase the risk of a crash.
Remedy: Toyota will notify owners, and dealers will perform a software update for the hybrid system. If the vehicle has experienced an inverter failure with certain hybrid system faults related to this condition, the inverter assembly will be repaired or replaced, prior to software update. All repairs will be performed free of charge. This recall began July 24, 2020. Owners may contact Toyota customer service at 1-888-270-9371. Toyota's number for this recall is 20TB10 / 20TA10.
Model-level recall history does not show whether a particular VIN is affected or has received a repair. Check a VIN with NHTSA ↗
NHTSA investigations
3
DP23005 · Brake Actuator Valve Wear
Opened Nov 22, 2023 · No close date supplied
Status: open (inferred from source dates) · Service Brakes, Hydraulic:foundation Components; Service Brakes, Hydraulic:power Assist
The Office of Defects Investigation (ODI) has received a petition dated September 19, 2023 from the owner of a 2012 Toyota Prius V requesting that ODI reevaluate its decision to deny DP19-004. In the letter, the petitioner reported experiencing an unexpected and complete loss of brake power while driving, accompanied by multiple dashboard warning lights. This petition is based on the petitioner's direct experience and assessment that ODI closed DP19-004 because its prompting petition was withdrawn by that petitioner. ODI will review the work conducted during DP19-004 and a review of any additional related complaints and crashes via a new defect petition The petition and related materials can be reviewed at NHTSA.gov under the following ODI number:11553736.
Additional source detail variants (2)
Service Brakes, Hydraulic:foundation Components
The Office of Defects Investigation (ODI) has received a petition dated September 19, 2023 from the owner of a 2012 Toyota Prius V requesting that ODI reevaluate its decision to deny DP19-004. In the letter, the petitioner reported experiencing an unexpected and complete loss of brake power while driving, accompanied by multiple dashboard warning lights. This petition is based on the petitioner's direct experience and assessment that ODI closed DP19-004 because its prompting petition was withdrawn by that petitioner. ODI will review the work conducted during DP19-004 and a review of any additional related complaints and crashes via a new defect petition The petition and related materials can be reviewed at NHTSA.gov under the following ODI number:11553736.
Service Brakes, Hydraulic:power Assist
The Office of Defects Investigation (ODI) has received a petition dated September 19, 2023 from the owner of a 2012 Toyota Prius V requesting that ODI reevaluate its decision to deny DP19-004. In the letter, the petitioner reported experiencing an unexpected and complete loss of brake power while driving, accompanied by multiple dashboard warning lights. This petition is based on the petitioner's direct experience and assessment that ODI closed DP19-004 because its prompting petition was withdrawn by that petitioner. ODI will review the work conducted during DP19-004 and a review of any additional related complaints and crashes via a new defect petition The petition and related materials can be reviewed at NHTSA.gov under the following ODI number:11553736.
DP22005 · Pedestrian Alert Sounds
Opened Jan 27, 2023 · Closed Aug 7, 2023
Status: closed (inferred from source dates) · Electrical System:propulsion System
NHTSA received a petition on or about July 18, 2022, requesting that Federal Motor Vehicle Safety Standard (FMVSS) 141 be applied to all electric and hybrid vehicles operating in the United States. The petition can be reviewed at NHTSA.gov under ODI Number 11486072. FMVSS 141 establishes performance requirements for pedestrian alert sounds for motor vehicles. The standard applies to hybrid and electric vehicles that have a gross vehicle weight rating of 4,536 KG or less or are defined as low-speed vehicles. The standard became fully applicable to all such vehicles manufactured on or after March 1, 2021.On January 27, 2023, NHTSA opened Defect Petition (DP) 22-005 to evaluate the subject matter described in the petition. On June 24, 2023 and as supplemented on June 25, 2023, the petitioner notified NHTSA he was withdrawing his petition. The petitioner indicated that, based on his review of data, there is no justification for asserting potential benefits that could be derived from actions sought by my petition. Based on the petitioner's withdrawal, DP22-005 is closed. Closure of this DP does not represent a determination by NHTSA regarding the subject matter of the petition.
DP19004 · Brake Actuator Valve Wear
Opened Sep 30, 2019 · Closed Jan 21, 2021
Status: closed (inferred from source dates) · Service Brakes, Hydraulic:power Assist
On September 19, 2019, the Office of Defects Investigation (ODI) received a defect petition from Mr. Roger Hogan requesting that the Agency investigate and recall certain Toyota Prius, Prius PHV, Camry Hybrid and Avalon Hybrid vehicles for a brake actuator valve wear condition covered under Toyota Customer Support Programs ZJB and ZKK (subject CSP?s). In support of his request, the petitioner identified 117 NHTSA complaints allegedly related to the subject CSP condition, including 60 reporting crashes. On September 30, 2019, ODI opened Defect Petition DP19-004 to evaluate the petitioner?s request for an investigation. In August 2020, the petitioner notified the Agency that he was withdrawing his petition. Because the petitioner has withdrawn the petition, we are denying the petition as moot and no further analysis of this petition is necessary.NHTSA is authorized to issue an order requiring notification and remedy of a defect if the Agency?s investigation shows a defect in the design, construction, or performance of a motor vehicle that presents an unreasonable risk to safety. 49 U.S.C. ?? 30102(a)(9), 30118. Because the petitioner has with withdrawn the petition, the petition is denied as moot. This action does not constitute a finding by NHTSA that a safety-related defect does not exist. The Agency notes that it is not required to receive a defect petition prior to opening a defect investigation and will take further action if warranted by future circumstances.
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