2017 Hyundai Sonata Plug-In Hybrid Problems

I am reporting a serious safety issue involving a 2017 Hyundai Sonata Plug-in Hybrid (VIN: [XXX] ), originally purchased in California. While driving at approximately 70 mph on a highway, the vehicle suddenly lost all propulsion without warning and rapidly decelerated. This created a dangerous situation with surrounding traffic and put me and my family at risk. I had to quickly maneuver to the shoulder to avoid a potential collision. The vehicle was towed to an authorized Hyundai dealership in Utah, where it was diagnosed with a failure of the high-voltage battery system. I was informed that the battery requires replacement. This type of sudden loss of propulsion at highway speed is extremely hazardous and could result in a crash, injury, or fatality. There were no prior warnings indicating an imminent failure of this severity. Given the safety risk associated with unexpected loss of propulsion, I am concerned this may represent a broader issue affecting similar vehicles. The vehicle is equipped with an interior camera, and video of the incident can be provided if needed. I respectfully request that this issue be investigated as a potential safety defect. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

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

On 12/20/25, the car - a Sonata plug-in hybrid - failed to start. When I pushed the "start" button, the dashboard display lit up w many clearly irrelevant error messages. Each time I pressed start, somewhat fewer error messages blasted toward me, and finally, no response at all. On 12/21/2026, the tow driver said it was the 12-volt battery. He gave us a jump start and we drove a few blocks. However, it failed at the turn lane while waiting for the light to turn. We turned it back on, bought a new battery, had it installed. On 12/29/25, my husband was driving. He turned into the intersection with a traffic light. As he was making the turn, the car simply quit. No warning. The car was dead, and blocking traffic! He pressed the start button to turn off the car, then again to turn it on. He was able to complete the turn and parked on the side of the road. By this time it had a "check engine" light on. He then drove slowly the few blocks back to our house. On 12/30/2025, the car was towed to a local mechanic. He said it threw the code PODE7, "almost certainly for a failed High Voltage battery." It was still under warranty, and we had the car towed to the dealership. After keeping it for 2 or 3 weeks, they confirmed the code and that the control panel needed to be replaced. We finally picked up the car (w new control panel) on 2/20/2026. In the meanwhile, we looked up Hyundai control panel repairs on a reddit forum. We found lots of chatter about it. Turns out it's a recognized problem in Sonata and Ioniq EV and PHEV's! Clearly, a car failing in the middle of an intersection, highway, etc is a safety problem and needs to have repair/replacements made BEFORE THEY HAPPEN!

While driving at a high rate of speed propulsion to the vehicle suddenly and without warning ceased, the electric and internal combustion engine were non-responsive (ICE stopped; hybrid motor didn't provide propulsion), the warning light said "Check Hybrid System. Turn off engine" I was put at risk because I was traveling at highway speed and was given no warning before the vehicle shut down. This has occurred nine times, I've reported all to Hyundai, they have had the car in the shop three times, the issue is not fixed. No, despite ODB2 error codes, the car has not shut down while a dealership is driving it. Yes, the vehicle has been inspected multiple times by Hyundai. Yes, always "Check Hybrid System. Turn off engine", in almost all cases the check engine light comes on after that, and in some cases additional lights such as "auto hold". This first occurred in Dec 2023, I was told the car was fixed (it wasn't) and happened again in October 2024. I haven't been able to drive my car since then.

While driving car stuttered check engine light and check hybrid system flashed. Check engine lights stayed on until getting home. Next day. I scanned and code p0b68 was set.

While driving at a high rate of speed propulsion to the vehicle suddenly and without warning ceased, the electric and internal combustion engine were non-responsive (ICE stopped; hybrid motor didn't provide propulsion), the warning light said "Check Hybrid System. Turn off engine" I was put at risk because I was traveling at highway speed and was given no warning before the vehicle shut down. This has occurred nine times, I've reported all to Hyundai, they have had the car in the shop three times, the issue is not fixed. No, despite ODB2 error codes, the car has not shut down while a dealership is driving it. Yes, the vehicle has been inspected multiple times by Hyundai. Yes, always "Check Hybrid System. Turn off engine", in almost all cases the check engine light comes on after that, and in some cases additional lights such as "auto hold". This first occurred in Dec 2023, I was told the car was fixed (it wasn't) and happened again in October 2024. I haven't been able to drive my car since then.

WHILE VEHICLE IS IN MOTION AT VARIOUS SPEEDS WITH CRUISE CONTROL ENGAGED CLIMBING UP ON HILLY OR STEEPER GRADES THE VEHICLE ACCELERATES ON THE DASH AT NEARLY 100 PERCENT POWER ACCORDING TO THE HYBRID TACHOMETER. THIS INCREASE IN POWER SURPASSES WELL OVER THE SET CRUISE SPEED. FROM WHAT I HAVE NOTICED ITS 6-10 MPH CLIMBING PAST MY SET SPEED. THERE IS ALSO A LONG DELAY IN POWER RESTORATION AFTER COASTING DOWN HILLS. I FOUND IT TO BE EXTREMELY DANGEROUS WITH THE VEHICLE AT 100 PERCENT POWER BECAUSE IT COULD CREATE A SITUATION IN WHICH YOU COULD POSSIBLY REAREND ANOTHER DRIVER OR LOSE CONTROL IN NORMAL OR ADVERSE DRIVING CONDITIONS, RESULTING IN INJURY OR LOSS OF LIFE. IN ADDITION THE ISSUE COULD LEAD TO A TRAFFIC INFRACTION. MY STATE HAS A LOT OF SPEED CAMERAS. THIS PROBLEM HAVE RESULTED FROM THE RECENT RECALL WHERE HYUNDAI INSTALLED A NEW BATTERY MANAGEMENT SYSTEM. THE VEHICLE HAS APROXIMENTLY 16400 MILES ON IT.

TL* THE CONTACT OWNS A 2017 HYUNDAI SONATA HYBRID. WHILE DRIVING APPROXIMATELY 20 MPH, THE FRONT SIDE COLLISION WARNING SYSTEM FAILED TO FUNCTION. THE VEHICLE WAS TAKEN TO STEVENS CREEK HYUNDAI (4425 STEVENS CREEK BLVD, SANTA CLARA, CA 95051), BUT THE FAILURE WAS UNABLE TO BE DIAGNOSED. THE VEHICLE WAS NOT REPAIRED AND THE FAILURE RECURRED. THE MANUFACTURER WAS NOT CONTACTED. THE APPROXIMATE FAILURE MILEAGE WAS 13,000.

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

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.

14 MARCH 2018 10:30 AM, 70 MPH ON US 101 TO SAN FRANCISCO, HEV MODE, RAINY WEATHER, 4 PASSENGERS FOR A BUSINESS MEETING. CAR STEERING SHUDDERED AS IF THE TIRES SLIPPED AND SPUN ON THE WET PAVEMENT. ESC, BRAKE, AND AUTO HOLD LIGHTS TURNED YELLOW. WAS ABLE TO DRIVE THE CAR NORMALLY TO REACH DESTINATION, PARKED, ATTENDED MEETING, AND STARTED DRIVING BACK HOME WITH MY PASSENGERS AT 3PM. ESC, BRAKE, AND AUTO HOLD LIGHTS WERE STILL ON. HEV MODE. 30 MINUTES LATER, I-280 AT 65+ MPH, ENGINE POWER DRASTICALLY REDUCED ABRUPTLY, CAR STARTED TO SLOW DOWN AND BECAME UNRESPONSIVE TO THE GAS. TURNED ON EMERGENCY FLASHERS AND WITH GREAT DIFFICULTY IN THE EVENING RUSH HOUR COMMUTE TRAFFIC, MANAGED TO SHIFT RIGHT THREE LANES AND TAKE THE NEXT EXIT, WENT INTO A PARKING LOT AND STOPPED THE CAR. CONSULTED MANUAL FOR ANY MEANINGFUL ACTIONS. STARTED CAR BACK UP. MIL LIGHT ALSO CAME ON ALONG WITH MESSAGE TO TAKE CAR TO DEALER. RAN VEHICLE DIAGNOSTICS AND GOT 'A POSSIBLE CONDITION WITH THE ECS HAS BEEN DETECTED AND A FULL SYSTEM CHECK IS RECOMMENDED SOON'. STARTED DRIVING CAR AGAIN. SAME LACK OF ENGINE POWER. DROVE THROUGH LOCAL ROADS AND COUNTLESS MANY TRAFFIC LIGHTS AND REACHED HOME AFTER 4 HOURS (NORMAL = 1 1/2 HOURS). AT HOME, PLUGGED CAR IN FOR CHARGING. CHARGING STARTED NORMALLY. AROUND 10PM, WANTED TO TAKE A PICTURE OF ALL THE LIGHTS, SO PULLED CHARGING CABLE OUT AND STARTED CAR. ALL LIGHTS WERE OFF EXCEPT MIL! DECIDED TO TEST DRIVE AND FOUND NO LOSS OF POWER. TOOK IT TO NEARBY FREEWAY, FLOORED GAS PEDAL. CAR RESPONDED WITH FULL POWER! NEXT DAY MORNING, DRIVING CAR TO DEALER, HEV LIGHT AND CONTINUOUS WARNING BEEP CAME ON, JUST A MILE AWAY FROM HOME.

I was driving the vehicle with 2 other occupants onboard on [XXX] towards US-101. The EPS warning light already came on after entering [XXX] from [XXX], but initially, I didn't think it was much of an issue. As I merged to the right lane in preparation of entering the highway, the steering began to feel very stiff, so I immediately made a right turn into a local street when there was a little bit of steering left. As soon as I pulled over, the steering locked up completely, and both the EPS warning light and the dash display's lane-departure system warning were activated. Luckily no other vehicle or humans were endangered at the time. I put the car into park and powered it off. When I powered it back on again several minutes later, the issue resolved itself and I was able to continue driving with normal steering, and steering remained normal after several power on/off cycles which included both local and highway driving. Come to think of it, ~3 months before this incident happened, I already noticed occasional stuttering of the steering wheel and humming of the EPS assembly when the car is stationary or at low speed. I took the car to a third-party repair shop on the next day since the Hyundai dealership appointment is a week away at the earliest. They ran diagnosis before telling me that the steering sensor in the EPS motor assembly failed, and this happened very frequently for 2017 Sonata Plug-in hybrids. This happens so often, apparently, that Hyundai issued service bulletin [XXX], but this very much looks like a recall to me, as when the system fails, steering is lost completely, and could cause great harm to myself as well as the occupants onboard, not to mention other vehicles around me. I was lucky that it happened before I entered the highway and also had a place to pull over. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)