My 2020 Hyundai Sonata has a recurring and dangerous defect involving sudden deceleration while driving. Without warning, the car abruptly slows to ~10 mph—often on the highway—while numerous dashboard warning lights activate. This poses an extreme safety risk to me, my passengers, and other drivers, as it forces me to maneuver off the road to avoid being hit. The issue began in January 2021, still with less than 4,000 miles and just five months after I purchased the car new. It has occurred repeatedly and unpredictably since then. I have taken the vehicle to a Hyundai-authorized dealer for repair on five occasions (January 2021; December 2021; January 2022; November 2024; and February 2025), but the problem has never been properly diagnosed or fixed. In November 2024, the issue occurred immediately as I drove off the dealer's lot, having been assured the vehicle was repaired and safe to drive. The most recent visit lasted over a month, yet the dealer could not replicate the problem and returned the car to me in early April 2025, without a clear resolution. The vehicle is currently in my possession and available for inspection. Each incident is accompanied by multiple warning lights (e.g., check engine, ESC, etc.) but no consistent diagnostic codes have been found. I’ve also found multiple similar complaints from other Sonata owners on the federal safety agency site, suggesting this may be a broader issue. This unresolved defect has made the vehicle unsafe to drive and caused significant emotional distress. I no longer trust the car or the assurances from Hyundai or the dealer that it is fixed.
2020 Hyundai Sonata driver assistance complaints
Page 2 of 2: complaints 11 to 22 of 22, newest first, as owners wrote them.
while driving my car on 3 different days the car slowed down, and the lights came EPB on, on the dashboard the EPB light came on the check engine light came on , forward collision light, auto hold light, slippery road light , and caution light with a ! mark.
While driving at about 45mph a warning flashed on my dash. I couldn't read it before it disappeared, but it was something about front collision., contact dealer. the car immediately lost all power. Everything was still running, but I had no acceleration. I had to back down a busy road into a vacant lot. I had just come off of the highway when this happened, if I had still been driving on the Highway, I would have been hit by a car from behind, since there was no warning at all. The car was towed to a Hyundai dealership. After a diagnosis, it was said to be the Throttle body. I had to wait for the repair because the part was on back order. I was told that there was another car there waiting on the same part. I am afraid to drive the car now, even though the repair was made. I feel this is a safety hazard, and that someone could be injured or killed because of this issue with the car.
I was driving Home from work and I fell a sleep behind the wheel and Hit a park car. The police report states that my impact speed was 50mph. My insurance company is very concerned that my Air Bags or sensors are defective and that I contact you immediately. Due to the damage and impact of the accident.
Tonight on 7/29/2023 after driving between 5-10 miles at night with very light traffic, my dashboard flashed a message telling me "Forward Safety system disabled. Radar blocked." After receiving this message and it clearing from the digital instrument cluster, a small triangle appeared with a exclamation mark. After driving between 1 to 5 miles further down the interstate the triangle cleared from the screen. There is no damage to the grill, or sensor, and no indication of mechanical issues as I was driving down the road. The grill and sensor both also have little to no dirt as I routinely wash my car each weekI have read through multiple other comments like me stating nothing whatsoever is on the front grill that could be obstructing the sensor. And like the other complaints, if there is no warning light, there is no code stored!
I first begin having an issue with the idle speed. It would jump up to 1,500 RPM, which is twice the normal 750 RPM level It started almost from the very beginning when I purchased this car new in early 2020. I mentioned it at first oil change at dealer at 3,500 miles. I was told it was normal. In the beginning it would come and go. Sometimes not happening for weeks in-between episodes. Then it started to have the check engine light come on after it would happen and stay on. I took it back while light was still on and they kept the car for several days. Said it was the EPV valve and replaced it. Car operated fine for a few days then started up again. It also started to idle up and down from 1500 down to 500 in a rapid succession. I was able to get it to stop sometimes by turning engine off and them back on. Again I contacted dealership and took car back in. They gave me a loaner car and kept my car for over a month. This time they replaced the computer they told me. I did not have car for more than a week before it started doing it again. It has gradually gotten worse and happens more often now. It has also started to have the Forward Collision Avoidance warning come on in addition to check engine light as well. Just this week it actually just died on me while driving and forced me to pull to side of road. Turn off the engine and restart the engine. This happen 3 times in succession. Dealership does not seem to have any idea on what is going on and have been not very helpful. 3 week wait to get an appointment to bring in and no loaner cars available. This problem with the 2020 vehicle is very dangerous. It can idle up at anytime and car will lurch, requiring forceful brakeing . Car dying while driving and losing power as well.
Whenever I am close to a Tesla in traffic or at a stoplight, my parking sensors go off. I believe that the frequency of my Sonata parking sensors is being interfered with by Tesla sensors. This could lead to unexpected braking in traffic. This problem has not been reproduced by a dealer or independent service center. It has not been inspected by the manufacturer, police, or insurance representatives. Warning sensors go off.
The contact leased a 2020 Hyundai Sonata. The contact state that the radar in the vehicle interacted with the radar in Ford vehicles. While parking in a parking spot there was a beeping sound detected. While at a stoplight with a vehicle in front to the side, the radar engaged when a Ford vehicle drove up. The contact stated while turning nearby another Ford vehicle the radar engaged and the driver applied the brakes. The Forward Collision-Avoidance warning light was illuminated. The contact called the local dealer, but the vehicle was not taken to be diagnosed or repaired. The manufacturer was not contacted. The failure mileage was approximately 6.
The driver seat belt pops out sometimes for reasons unknown. The speakers suddenly stop working at random times so I got lost while listening for navigation directions safely paying attention to the road instead of watching the screen for upcoming turns. And the biggest one, a few times I almost crashed into oncoming cars and guard rails because if the road has a dip the sonata decides to jerk hard to the side and overcorrect itself when lane assist is on. When the road is level it just beeps annoyingly loudly when it can't see the lines or you accidentally cross over it, but does not actively assist even tho active lane assist is on. This is a major safety issue!!!!!
Gases from the dashboard heating cause a film to form between the windshield and the camera. Because of this, in heavy direct sunlight, lane keep assist toggles on and off without warning causing unintended lane departures with out warning. Also, when using smart cruise control, the vehicle slows to a stop but may continue moving slowly even after displaying the press gas to continue screen. The auto hold light does not illuminate.
I own a 2020 hyundai sonata. I purchased the car on january this year the miles in the car is 700 miles. A month after the car star giving me problem with break. Somehow the car applies the emergency break by itself and doesn't want to move. When I drive the car suddenly stop by itself and giving me message like: to move the car put your seat belt, lock all the door even when I have my seatbelt and doors are lock the car do that when ever the less I expected. I took the car three time for repair and update and the car give me the same problem. The dealer gave me a loaner another 2020 sonata and have the same problem. This is a very dangerous issues because if is rainy or snowing. The dealer doesn't find anything wrong with the car when they drive the car. I told them that happen when the lees expected
Tl* the contact owns a 2020 hyundai sonata. The contact stated that while driving at various speeds, the passenger's side blind spot detection system failed to activate. The contact also stated that the forward collision warning light intermittently activated while stopped at a red light. The contact stated the rear brake assist activated intermittently on several occasions. The vehicle was taken to nassief hyundai located at 1059 oh-46 north, jefferson, oh 44047, and preston hyundai of sharon located at 1251 e state st, sharon, pa 16146, where the mechanics were unable to duplicate failure. The vehicle had not been diagnosed nor repaired as of yet. The manufacturer had not been informed of failure. The failure mileage was approximately 623. *bf
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