2019 Toyota Prius Brakes Problems

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Since October 2023, my 2019 Toyota Prius has developed severe and unpredictable driving behavior after a regular brake service, which may have triggered or coincided with a software or ECU update. The car, which had been driving smoothly since I bought it in 2021, suddenly began showing false braking, steering interference, and lane instability — as if the car were trying to “correct” problems that didn’t exist. These interventions often happen on highways or during turns, creating serious safety risks for both driver and passengers. I’ve spent months and thousands of dollars replacing parts, performing alignments, and recalibrating sensors, including at Toyota dealerships. The problem persists because it is software-based, not mechanical. I discovered that in mid–2023, the NHTSA announced upcoming rules requiring Automatic Emergency Braking (AEB) with pedestrian detection by 2029. Around that same time, reports from multiple drivers (Toyota, Honda, Hyundai, Ford, Subaru) began to appear describing the exact same issues. It seems manufacturers began silently updating vehicles to meet anticipated compliance standards. However, this introduced overly sensitive and malfunctioning driver-assist systems. The most alarming part is that the driver cannot fully disable these features — the “off” button only reduces their intervention. This means when the system malfunctions, the driver is forced to operate an unsafe vehicle. As a professional rideshare driver, this problem destroyed my ability to work. Passengers reported me for unsafe driving because of the car’s erratic behavior. I eventually lost my vehicle and income. I believe this is a systemic safety defect linked to premature or unregulated implementation of AEB software. Drivers deserve the right to fully disable malfunctioning systems that endanger lives. This is not just a car issue — it’s a public safety crisis that must be urgently investigated.

The contact owns a 2019 Toyota Prius. The contact stated that upon depression of the brake pedal, pulsation in the brake pedal could be felt without warning. Upon taking the vehicle to a dealer, he requested to have the rotors checked for any defects. He was given a service report that stated that the rotors needed to be replaced. Upon taking the vehicle home, the contact inspected the vehicle himself and discovered corrosion on all four of the brake rotors. The contact took the vehicle back to the dealer where they confirmed the failure and informed him that there were no recalls on the vehicle and that the brake rotors were not covered under warranty. The manufacturer was notified of the failure and he filed a complaint. The vehicle had yet to be repaired. The failure mileage was approximately 11,000.

I WAS TRAVELING AT ABOUT 55 MPH ON HIGHWAY 66 WHEN THE INSTRUMENT PANEL BEGAN FLASHING THE FOLLOWING WARNINGS: "BRAKING POWER LOW, PHSB MALFUNCTION, PARKING BRAKE LOW, PRE-COLLISION MALFUNCTION, ANTI-LOCK MALFUNCTION, LANE DEPARRURE MALFUNCTION, BRAKE OVERIDE" . THE ONLY OBVIOUS SYMPTOM WAS THAT THERE WAS NO BRAKE BOOST - THE BRAKES CONTINUED TO FUNCTION, BUT WITHOUT POWER ASSIST. I AM A FORMER AUTO MECHANIC, SO I WOULD HAVE NOTICED IF THERE WERE ANY OTHER SYMPTONS. THE DEALERSHIP HAD THE CAR FOR 3 WEEKS AND ULTIMATELY REPLACED BOTH THE BRAKE BOOSTER AND THE MASTER CYLINDER. THEY INITIALLY REPLACED THE BOOSTER AND DISCOVERED THAT THAT DID NOT FIX WHATEVER WAS CAUSING THE WARNINGS AND DTCS. TOYOTA INSTRUCTED THEM TO REPLACE THE MASTER CYLINDER AND THAT APPARENTLY FIXED THE PROBLEM. THEY COULD NOT EXPLAIN WHY A FAULT IN THE MASTER CYLIDER WOULD HAVE CAUSED THE ARRAY OF SYMOTOMS OBSERVED BY BOTH MYSELF AND THE MECHANICS. I WAS SURPRIZED THAT THE MASTER CYLINDER WAS THE CAUSE AS THE THE LOSS OF BOOST SEEMED TO BE A BRAKE BOOST PROBLEM. I WAS TOLD THAT TOYOTA IS AWARE OF THE PROBLEM AND THAT IT IS WIDESPREAD.