2011 Toyota Prius: ABS light or ABS activating

Filed Aug 10, 2026 · Brakes · IA

Vehicle Information: 2011 Toyota Prius, 144,000 miles. Component: Hydraulic Service Brakes, Electronic Stability Control, Anti-lock Braking System. Description of Incident: While driving at normal speeds, the vehicle suddenly experienced a severe reduction in braking capability. The dashboard simultaneously illuminated the Brake Warning Light, ABS Light, and Slip/Traction Control Indicator Light. The brake pedal immediately became soft, spongy, and squishy, requiring significantly increased physical foot pressure and a vastly extended distance to bring the vehicle to a stop. Upon inspection, the brake fluid reservoir remains completely full, but the brake booster pump under the hood cycles and buzzes rapidly every 10 seconds while stationary. A diagnostic scan confirmed trouble code C1391 (Brake Actuator Internal Leak). This indicates a severe internal hydraulic pressure bleed inside the braking module. [SEE ATTACHED] This is a known, widespread manufacturing defect previously documented under Toyota Customer Support Program ZJB. The manufacturer has refused to remedy this life-threatening safety defect because a 10-year calendar threshold has passed, despite the vehicle being well under the 150,000-mile limit established by the manufacturer. The vehicle currently poses an immediate safety risk to occupants and the public.

Filed Jul 26, 2026 · Brakes · TX

Every time I'd press the brakes there'd be an audible "click" noise and then when taking my foot off the brake it'd sound like a manual tire pump being pressed... kind of like air filling / hydraulic sound. This worried me (I don't mess around with brakes). One other thing that would happen is if I pressed the brake hard enough, the automatic braking system would kick in. The Toyota dealership claimed they couldn't hear anything and there were no warning lights so I took it to a reputable local mechanic. They diagnosed it as a bad ABS Actuator / Brake Booster and said it's common with this year of Prius. They also said it was good I brought it in now because it was not severe enough to totally fail (which could have caused an accident) but there was evidence of degradation and they also said the issue was causing sufficient brake fluid to not get where it needs to be.

Filed Jun 26, 2026 · Brakes · CA

Vehicle Information: Year: 2011 Make: Toyota Model: Prius Mileage at Failure: 58,769 miles Date of First Use: February 20, 2012 Complaint Description: As I was driving on the freeway, my 2011 Toyota Prius brakelights all came on. I pulled off, had it towed to nearest mechanic, who diagnosed a failure involving the brake booster, brake actuator, and ABS system at only 58,769 miles. The vehicle was diagnosed with Diagnostic Trouble Code C1391 (Abnormal Leak of Accumulator Pressure). According to my mechanic, the condition is caused by an internal brake fluid leak within the brake booster assembly with master cylinder. The recommended repair includes replacement of both the brake booster assembly with master cylinder and the brake booster pump assembly. The estimated cost of repair is approximately $4,100. This concerns me because the brake system is a critical safety component, and I believe such a failure at fewer than 60,000 miles is highly unusual and may pose a safety risk to drivers and passengers. Toyota previously issued a Warranty Enhancement Program for this issue, but my vehicle was denied coverage because the program expired on August 31, 2021, and the secondary coverage expired on February 20, 2022, ten years after the vehicle's first use date. Toyota declined any out-of-warranty assistance despite the vehicle's exceptionally low mileage. I am submitting this complaint so that this incident is documented as a potential safety concern involving premature failure of the brake booster and ABS system components on the 2011 Toyota Prius.

Filed Jun 18, 2026 · Brakes · NC

Shortly after purchasing used last year I had my brake, traction control, ABS, & TPMS lights come on when stopping at a stop light all at once. I went and had it scanned and no codes showed up. I hear a buzzing from the brake actuator/ brake pump every 15 seconds. This all has been going on for almost a year now. Over the weekend a loud buzzing warning alarm came on that will not turn off. I had it checked out and was quoted around 3500 to repair.

Filed Jun 16, 2026 · Brakes · SC

The ABS actuator (brake booster) went out suddenly. It is 100% available for inspection. It is being towed to M&M Auto Repair in Gaston SC. I was not sure if the car was going to stop when I was trying to figure out what was wrong. The car was acting like it wasn't going to stop until a few seconds later. People online have had a similar problem as me with prius models around my year to 2015. And it was a problem confirmed by the dealership. The component has not been inspected. Only diagnostics were ran. The ABS system light came on. But it would disappear for a long time then come back. So I thought it was a computer error for the longest until it proved to not be one. Because the brakes were working just fine like normal. Other than that, the light itself was playing peekaboo with me, making me believe that it was a computer error since the brakes were working just fine. Then on monday, the car started beeping excessively and the brakes were not working suddenly after being fine over the weekend....with no issues.

Filed May 9, 2026 · Brakes, Driver assistance · NY

2011 Prius. 80k miles. Brake booster buzz coming on every 15 seconds now. ABs, traction and brake lights on. I’ve heard of many Prius owners with the same issue. I also have another Prius with the same issue at 120k miles. Brake booster accumulator codes popping up with 80k miles. It is a safety concern as the abs brakes don’t work. Almost every Prius is effected by this.

Filed Apr 27, 2026 · Acceleration, Brakes · TX

I was driving my car and suddenly the traction , hand brake and ABS sign started showing up. I usually apply only 10% of force on brake pedal but after this I have to apply almost 60% of force to even slow down the car. Almost 90% force to stop the car It has threatened safety of my family. When diagnosed at autozone they told cannot determine error code. When reading in internet this seems to be common problem in prius. Please help is fixing the issue as it is not at my fault. This seems to be manufacturing defect.

Filed Apr 16, 2026 · Brakes · CA

Brake Booster went out right at 160000 miles. ABS, emergency parking light, tire pressure light, and others I'm not sure if went on. Brakes felt very mushy and scary to drive.

Filed Feb 2, 2026 · Brakes · CA

While driving, the Brake, ABS, traction light and other light lit up. The car lurched in an odd way. I can hear the oil pressure pump turn on every 5 seconds. Toyota shops told me the master cylinder and booster pump are failing and that the brakes will stop working while driving, causing an accident.

Filed Jan 14, 2026 · Brakes · MD

The abs, brake, and traction control are intermittently on and off recently. I thought that there was a visible leak in the brake fluid. But my mechanic said that there was no feasible leaks found upon inspection. The car has also been inspected in Maryland without any issues. I came across many forums that said that this is a common issue in Prius. My safety was at risk if this is due to internal failure or defect of the product, especially because I drive with my [XXX] almost everyday to take her to daycare. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Dec 28, 2025 · Brakes · VA

ABS, Slip Indicator and Brake warning lights have appeared on the cars dashboard. DTC fault code C1391 has appeared indicating a failure of the Brake Booster and Brake Booster Pump assemblies per Toyota Customer Support Bulletin (ZJB) No.: POL18-03. Loss of regenerative braking, putting the safety off occupants at risk.

Filed Nov 18, 2025 · Brakes · WA

I purchased a 2011 Prius 4 years ago from a dealership. For the last 2 years, whenever I drive the car, the ABS, brake, and skid lights are on. also, there's a slightly whirring noise every few seconds from under the hood. Braking has been affected, and I've had to increase my stopping distance as a result. Also, the brake pads and rotors deteriorate faster. Apparently, this is a common problem with this type of car. I've called Toyota, and despite it being a known flaw with this car, they refuse to do anything about it.