Warnings problems of the 2020 Hyundai Sonata

My 2020 Hyundai Sonata has a recurring defect in its engine or transmission, causing sudden deceleration to ~10 mph without warning, often on major highways, with warning lights (check engine, esc, traction control, etc. ) flashing seconds before the car decelerates. This forces me to swerve off busy roads, endangering me, my passengers, and other drivers. Near-misses with traffic pose an extreme safety risk, causing significant emotional distress. The car, at a Hyundai dealer since April 21, 2025, is available for NHTSA inspection. The issue began in January 2021, five months after purchase, with all the warning lights appearing during incidents along with rapid deceleration. The Hyundai dealer confirmed the problem in seven repair attempts (January 2021, December 2021, January 2022, November 2024, February 2025, and twice in April 2025) but never properly diagnosed or fixed it, citing no consistent diagnostic codes. Only the dealer assessed it; no inspections by Hyundai’s manufacturer, police, or insurance occurred. In November 2024, the defect recurred immediately after pickup, despite false assurances it was fixed. In February 2025, the dealer kept the car over a month with minimal communication, yet it failed again. I picked up the car on April 4, 2025, but it broke down on April 6, less than 55 hours later. I returned it April 7 and picked it up April 17, and it failed again on April 21, 2025 with the vehicle remaining at the dealer since. The dealer and Hyundai offer no solution and this dangerous issue keeps recurring. Similar NHTSA complaints suggest a broader issue. Rapid recurrences—hours after April 4 and four days after April 17—prove the car is unsafe and assurances of repairs are untrustworthy. I no longer trust the Sonata or Hyundai’s repairs, as the defect persists.

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, just five months after I purchased the car new. It has occurred repeatedly and unpredictably since then. I have taken the vehicle to Hyundai-authorized dealers 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 after I picked the car up from the dealership when they told me it was fixed and ready to drive. This most recent occurrence (February 2025) before tonight's incident on April 6, 2025, the dealer had my vehicle for over a month. During this time, communication was seldom initiated by the dealer. Now the problem recurred less than 55 hours after picking the vehicle up from the Hyundai certified dealer, who told me the issue was fixed and the car looks and runs great. Unfortunately I found myself in this dangerous situation despite the dealer's reassurances and Hyundai's involvement overseeing the repair process. The unsafe, defective Sonata is currently in my possession as I figure out next steps. Each incident is accompanied by multiple warning lights (e. G. , check engine, esc, etc. ) but the dealer represents that no consistent diagnostic codes have been found. I’ve also found multiple similar complaints from other Sonata owners on the NHTSA 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.

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 NHTSA 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.

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.