What 32 owners told NHTSA about the 2017 Hyundai Sonata Plug-in

To the National Highway Traffic Safety Administration, I am filing this formal safety complaint regarding a dangerous engine failure incident involving my 2017 Hyundai Sonata Plug-in Hybrid. Description of Incident: While traveling on CA-85 near Mountain View, California, at approximately 65 miles per hour, the engine suddenly and without warning lost all power. The vehicle began to slow down involuntarily in active highway traffic, creating an immediate and serious risk of rear-end collision. The driver had no ability to maintain safe highway speed or accelerate out of danger. The vehicle had to be towed from the scene to the dealership. There was no warning light or prior indication that engine failure was imminent. The failure was sudden, complete, and occurred at highway speed in heavy traffic conditions. Safety Risk to the Public: This incident represents a significant and ongoing public safety hazard. A sudden, unpredictable loss of engine power at highway speed — with no prior warning — places the driver, passengers, and surrounding vehicles at serious risk of collision. This is not an isolated mechanical inconvenience; it is a life-threatening failure mode. Known and Documented Defects: The 2017 Hyundai Sonata Plug-in Hybrid has been the subject of multiple recalls and class action litigation related to engine defects. My incident is consistent with the known failure patterns documented in those proceedings. Despite this history, Hyundai Motor America has denied my warranty claim, citing missed services — a characterization I dispute, as the vehicle was serviced exclusively at an authorized Hyundai dealership whenever the onboard system indicated service was due, and no technician ever identified or disclosed any engine damage during those visits. Request to NHTSA: I respectfully request that NHTSA: 1. Open or expand an investigation into engine failure incidents in the 2018 Hyundai Sonata Plug-in Hybrid 2. Investigate whether a recall is warranted

NHTSA ODI 11725213

While driving the 2017 Hyundai Sonata Plug-In Hybrid, the car will begin to stall, a rapid number of audible beeps will start, the "Check Hybrid System" notification will pop up on the dashboard, and the "Check Engine Light" appears.. The car therefore cannot be driven anymore, and I am forced to pull over to the side. In order to fix the issue temporarily, I need to turn the car off and turn it back on again. Once this is completed, both the "Check Hybrid System" and the "Check Engine Light" disappears and the car can be driven again. An OBD Scanner is unable to find exactly what is going on as the "Check Hybrid System" and the "Check Engine Light" no longer appear. This has happened 4 times now within the span of 3 months. The people at risk are me (the driver), my passengers, and potentially everyone else on the road in my nearby vicinity as the problem occurs. This problem has been confirmed by the dealer in their Hybrid vehicles. This vehicle has not been inspected yet but that is an ongoing process.

NHTSA ODI 11579536

I WAS DRIVING MY HYUNDAI 2017 SONATA PLUGIN HYBRID ON THE HIGH WAY IN HEV MODE AND SUDDENLY I FELT SEVERE VIBRATION IN MY CAR. THEN I CHANGED MY ENGINE TO EV MODE AND IT WAS FINE. ENGINE LIGHT CAME ON. EVERY TIME THE GAS ENGINE CAME ON THE CAR STARTED VIBRATING AND NON RESPONSIVE TO GAS. I DROVE ABOUT 10 MORE KM TOWARDS HOME ON ELECTRIC ONLY ENGINE AND THEN GOT IT TOWED TO THE DEALERSHIP. IT FELT LIKE ENGINE LOST ITS POWER. I RECENTLY CHANGED THE VOLTAGE PROTECTION DEVICE ON THE CAR AS A RECALL. ALL SERVICES WERE DONE ON TIME AND CAR HAD ONLY 33000 KM.

NHTSA ODI 11210126

2017 HYUNDAI SONATA PLUG IN FEATURE FORWARD COLLISION WARNING ON FRONT STICKER SHOULD HAVE ALSO SAID IT ONLY WORKS ABOVE 25MPH AND IT DOES NOT ACTIVATE WARNING SOON ENOUGH SO I THINK ITS CRASH ZONE AND SHOUDL BE ADJUSTABLE AND TESTABLE IT IS NOT NTSB I HOPE CAN HELP MANUFACTURE A STANDARD TERMINOLOGY WHEN IT COME TO SALES AND RELEASE OF HYUNDAI LIABLE IN CASE FAILURE , YES I KNOW THEY WILL NOT COVER FAILURE UNDER MANY CONDITIONS, BUT THE SYSTEM I BROUGHT TO HYUNDAI 2X ONE IN JULY 2017 AND ONE IN MAR 2018 I WAS TOLD FRONTSIDE COLLISION WORK , THERE ARE NO ADJUSTMET FOR DISTANCE VS SPEED TECH JUST TAKE ME FOR RIDE ALMOST COLLIDE WITH THE CAR BEFORE THE COLLISION WARNING CAME ON IT SHOULD HAVE COME ON WITHIN 1-2 SECOND RULE, AND HYUNDAI HAS CHANGE THE SYSTEM FOR YEAR 2018 ,, I'M WORK WITH HYUNDAI TO GET PROPER LABEL , AND RETURN CAR FOR NTSB THE STICKER SHOULD BE MADE TO STATE TYPE OF SYSTEM AND HYUNDAI SHOULD ASK CONSUMER TO SIGN LIABLE RELAEASE THAT SYSTEM WONT ALWAYS WORK, HYUNDAI IS WORK WITH ME, SO THANKS, BUT NTSB SHOUD TEST FRONTSIDE COLLISION SYSTEMS RATE THEM TECHS SHOULD NOT HAVE TO DRIVE THE CAR INTO A CRASH ZONE TO TEST IT, AND I SHOULD BE TOLD SYSTEM NOT WORK<25MPH EVASIVE SALE BUT HYUNDAI WORK WITH ME FYI EXAMPLE OF GOOD SYSTEM IS MOBILEYE 630 FOR FRONTSIDE

NHTSA ODI 11091575