2021 Hyundai Sonata Hybrid problems

“The vehicle experiences sudden, complete electrical power loss while driving at speed on highways and city streets or on the parking. All digital displays turn off, the engine shuts down, and power-assisted steering and braking are instantly lost without prior warning, presenting an extreme collision risk. The issue first occurred in August 2025 at approximately 48,000 miles and was taken to an authorized Hyundai dealer in Michigan for warranty repair. The dealer held the vehicle for over 30 days but failed to correct the defect. The identical power failure has continued and recently escalated to daily occurrences. A second Hyundai dealer (Pacifico Hyundai, Philadelphia, PA) diagnosed an intermittent open circuit in the engine wiring harness but Hyundai Motor America refuses to repair the vehicle under warranty, claiming 'outside influence' without providing evidence. Driving a hybrid vehicle that randomly cuts all power in live traffic is a life-threatening safety hazard. Hyundai Motor America has failed to rectify this critical safety defect.”

“Overheated engine alarm came on while I was on the freeway on a rainy day. Vehicle was towed to Hyundai dealership in which service technician found that the part preventing water from leaking into the muffler was broken. Hyundai dealership has ordered replacement part but it is on backorder. The broken part that needed replacement has been on backorder for close to a month and there is not an ETA of when the part will be received. Prior to the overheated engine alarm going off, cold air was blowing out of the vents even when the heat option was selected.”

“My Lincoln Nautilus (9,180 miles) logged 6 "Powertrain Malfunction / Reduced Power" alerts in the [XXX] telematics system between XXX (XXX at 7:59 PM and 8:16 PM; XXX at 1:07 PM and 1:39 PM; XXX at 11:16 PM; and XXX at 10:56 AM). Out of the 6 logged events, I experienced severe loss of motive power during two of them. On XXX, while driving 70 mph on I-95, the vehicle completely lost all propulsion. Coasting without power, I was unable to pull fully onto the shoulder, leaving the car partially stuck in active traffic and narrowly escaping a high-speed collision. Once stopped, the vehicle failed to recognize that it was in Park, causing the electronic parking brake to lock without releasing, which severely delayed towing recovery. The vehicle was towed to a Lincoln dealership in [XXX], whose service department was closed. Upon arrival, the vehicle suffered a complete electrical blackout; the key fob would not unlock the doors, requiring physical key entry. A sales representative provided a jump box, allowing me to start the car, drive back to [XXX], and deliver it to Cavalier Lincoln Ford in [XXX] between 5:00 PM and 7:00 PM on XXX. Cavalier Lincoln Ford stated…”

“While driving, engine alerted that it was overheating. Pulled over and coolant was very low, so I refilled it and then while driving to my family's garage to use the lift, saw white exhaust smoke. Took it to an independent mechanic, and in the ~10 mile trip there, over a quart of coolant had been burned off. He was able to reproduce the issue. No issues with the engine operation, it runs well and efficient, no check engine light. Mechanic found that a coolant line runs to the middle of the exhaust system and that this seems to be the issue. Other owners seem to have reported this same issue with this same model and roughly the same year, in which the muffler assembly needs replaced due to coolant leaking into the exhaust. Only prior issue was less warm air out of the vents for the previous week or so, but no other issues or warnings.”

“See attached document for complaint.”

“On three separate occasions, while going very fast (60-78 mph), the automatic emergency braking system turns on. The warning lights flash and there is some type of warning noise. I don't even know if it starts to break because it scares me so much, I just press the gas. It turns off within a couple of seconds, but that is not the point. If I didn't react so fast, I am unsure of what could actually happen.”