2019 TOYOTA PRIUS Service 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.

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.

* I was pulling into a parking space at a slow speed. When I applied the brake the car accelerated causing the car to scrape the car next to the space. The car then stopped. * The acceleration was out of my control and the brakes did not stop it. Fortunately there was no person in front of me. * The Tow truck operator who came to get the car experienced the same issue when pulling into the bay at the dealer. I do not know about the manufacturer during their inspection as they did not provide me with that information. * Toyota had an inspection performed and that report was submitted to Toyota on August 20. We just received notification from Toyota that they found no problem with the car. * No warning lights noted.

* I was pulling into a parking space at a slow speed. When I applied the brake the car accelerated causing the car to scrape the car next to the space. The car then stopped. * The acceleration was out of my control and the brakes did not stop it. Fortunately there was no person in front of me. * The Tow truck operator who came to get the car experienced the same issue when pulling into the bay at the dealer. I do not know about the manufacturer during their inspection as they did not provide me with that information. * Toyota had an inspection performed and that report was submitted to Toyota on August 20. We just received notification from Toyota that they found no problem with the car. * No warning lights noted.

I was idling at a parking space and went to turn off my car. The vehicle surged forward and the BRAKE sign came on. I pushed my brake to the floor and nothing happened. I was moving toward a brick wall so I put in in reverse and the car surged backwards. The BRAKE sign came on and I pushed the brake to the floor and again nothing happened and I ended up hitting the car behind me. I immediately took my car to the dealership where they kept it for 3 days and said they could find nothing wrong and it was safe to drive. I just got it back from having the body work done and am afraid to drive it as this might happen again or worse. I am reporting it to let you know and to see if this has occurred and been reported as happening in this make and model previously. I also have 2 witnesses to what happened.

I was idling at a parking space and went to turn off my car. The vehicle surged forward and the BRAKE sign came on. I pushed my brake to the floor and nothing happened. I was moving toward a brick wall so I put in in reverse and the car surged backwards. The BRAKE sign came on and I pushed the brake to the floor and again nothing happened and I ended up hitting the car behind me. I immediately took my car to the dealership where they kept it for 3 days and said they could find nothing wrong and it was safe to drive. I just got it back from having the body work done and am afraid to drive it as this might happen again or worse. I am reporting it to let you know and to see if this has occurred and been reported as happening in this make and model previously. I also have 2 witnesses to what happened.

On Saturday [XXX], while shifting to reverse in a back alley to back up slowly, the car engine suddenly and loudly revved and shot backwards at accelerating speed. I slammed on brakes which did not respond at all, thus forcing me to attempt to shift gears which also failed to stop the acceleration. Car only stopped because it went up a curb and hit the corner of a parked vehicle in a neighbors driveway. If I had been on busier street and not a back alley this could have resulted in numerous vehicle collisions and unimagined fatalities. Car is being towed on [XXX] to Advanced Collision Repair on 4511 Central Ave, Columbia Heights, for diagnostic assessment. There were no warning lamps, messages or other indicators prior to this terrifying lack of vehicle control . This was first episode since purchasing car approx one year ago. Incident was captured on neighbor’s home camera. Other neighbor heard the revving and ran out due to spontaneously loud revving of an engine. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

On Saturday [XXX], while shifting to reverse in a back alley to back up slowly, the car engine suddenly and loudly revved and shot backwards at accelerating speed. I slammed on brakes which did not respond at all, thus forcing me to attempt to shift gears which also failed to stop the acceleration. Car only stopped because it went up a curb and hit the corner of a parked vehicle in a neighbors driveway. If I had been on busier street and not a back alley this could have resulted in numerous vehicle collisions and unimagined fatalities. Car is being towed on [XXX] to Advanced Collision Repair on 4511 Central Ave, Columbia Heights, for diagnostic assessment. There were no warning lamps, messages or other indicators prior to this terrifying lack of vehicle control . This was first episode since purchasing car approx one year ago. Incident was captured on neighbor’s home camera. Other neighbor heard the revving and ran out due to spontaneously loud revving of an engine. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

VEHICLE INVOLVED IN A ACCIDENT. VEHICLE BRAKE SYSTEM DID NOT WORK. DRIVER HAD FOOT ON BRAKE PEDAL. ANTI COLLISION BREAK SYSTEM DID NOT WORK, VEHICLE SLID FOR 20FT INTO A STOPPED FOR. 2019 PRIUS WAS GOING 35 MPH BEFORE RISK OF COLLISION WAS REALIZED. SIGNIFICANT DAMAGE DONE ON PASSENGER SIDE BUMPER. NO AIR BAGS DEPLOYED.

VEHICLE INVOLVED IN A ACCIDENT. VEHICLE BRAKE SYSTEM DID NOT WORK. DRIVER HAD FOOT ON BRAKE PEDAL. ANTI COLLISION BREAK SYSTEM DID NOT WORK, VEHICLE SLID FOR 20FT INTO A STOPPED FOR. 2019 PRIUS WAS GOING 35 MPH BEFORE RISK OF COLLISION WAS REALIZED. SIGNIFICANT DAMAGE DONE ON PASSENGER SIDE BUMPER. NO AIR BAGS DEPLOYED.

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.

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.

I WAS TURNING TO EXIT A FREEWAY AND ALL OF A SUDDEN MY CAR CAME TO A STOP (ABOUT 55MPH TO 0) IN A MATTER OF SECONDS WITH NO WARNING. IT THEN TOOK A FEW SECONDS BEFORE I WAS ABLE TO GET THE GAS TO WORK AGAIN. NO CARS WERE AROUND ME LUCKILY.

I WAS TURNING TO EXIT A FREEWAY AND ALL OF A SUDDEN MY CAR CAME TO A STOP (ABOUT 55MPH TO 0) IN A MATTER OF SECONDS WITH NO WARNING. IT THEN TOOK A FEW SECONDS BEFORE I WAS ABLE TO GET THE GAS TO WORK AGAIN. NO CARS WERE AROUND ME LUCKILY.

BOUGHT A NEW 2019 PRIUS FROM GROSSINGER TOYOTA ON 9/13, WENT BACK TO THE DEALER ON 9/16 TO GET MY OLD CITY STICKER FROM MY OLD CAR (THIS NEW CAR ONLY HAD 61 MILES), THE NEW CAR BROKE WHILE I WAS THERE. THE ENTIRE DASHBOARD WENT OFF (BLINDERS CANNOT BE TURN ON. NO INDICATION OF SPEED, NO INDICATION OF VEHICLE LEVEL, ETC). ANYTHING THAT'S ON THE DASHBOARD WENT BLANK. I TURNED ON AND OFF THE NEW CARD A FEW TIME, BUT THE RESULT WAS THE SAME. TOYOTA TECHNICIAN COULDN'T FIGURE OUT WHAT WENT WRONG THEMSELVES. WHEN THAT HAPPENED, I WAS JUST ABOUT READY TO LEAVE THE DEALER, THEN I QUICKLY WENT BACK TO SHOW THE GROSSINGER DEALER.

BOUGHT A NEW 2019 PRIUS FROM GROSSINGER TOYOTA ON 9/13, WENT BACK TO THE DEALER ON 9/16 TO GET MY OLD CITY STICKER FROM MY OLD CAR (THIS NEW CAR ONLY HAD 61 MILES), THE NEW CAR BROKE WHILE I WAS THERE. THE ENTIRE DASHBOARD WENT OFF (BLINDERS CANNOT BE TURN ON. NO INDICATION OF SPEED, NO INDICATION OF VEHICLE LEVEL, ETC). ANYTHING THAT'S ON THE DASHBOARD WENT BLANK. I TURNED ON AND OFF THE NEW CARD A FEW TIME, BUT THE RESULT WAS THE SAME. TOYOTA TECHNICIAN COULDN'T FIGURE OUT WHAT WENT WRONG THEMSELVES. WHEN THAT HAPPENED, I WAS JUST ABOUT READY TO LEAVE THE DEALER, THEN I QUICKLY WENT BACK TO SHOW THE GROSSINGER DEALER.