2020 Hyundai Sonata: multiple warning lights

Filed Nov 2, 2026 · Driver assistance, Electrical · UT

My 2020 Hyundai Sonata has a recurring electronic system malfunction that causes multiple dashboard warning lights to illuminate, including the Forward Collision-Avoidance Assist System warning. When this occurs, the vehicle can suddenly lose the ability to accelerate. Most recently, this happened while driving in rainy conditions, creating a serious safety hazard. The vehicle has undergone multiple unsuccessful repairs at Hyundai dealerships, including an extended four-week repair involving Hyundai's technical specialists in 2025. The same problem has now returned, and I am concerned about the vehicle's safety and reliability.

Filed May 4, 2025 · Driver assistance, Electrical · TX

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 the federal safety agency 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 the federal safety agency 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.

Filed Apr 6, 2025 · Driver assistance, Electrical · TX

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.

Filed Apr 6, 2025 · Driver assistance, Electrical · TX

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 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.

Filed Apr 11, 2021 · Engine · 1,389 miles · NY

On nov. 17 while driving app. 65 MPH on the highway the car suddenly shut itself off. All of the dashboard lights lit up & the car would not restart. After 10 min. Of trying to restart the car, the car started again, & all the lights on the car disappeared. The following day, while waiting in the turning lane at a red light, the car sputtered & turned off. All the lights on the dashboard lit up & the car wouldn't start I had the car towed on nov 18 202 to a hyundai dealership. The dealership reported that there was an internal short with the ABS module & the hydraulic module assembly was replaced. On, nov 24, I was driving the car & the car stalled all the warning lights went back on. I had the car towed the dealership where it stayed until december 11 the dealership stated that they could not find anything wrong with the car. I picked up the car on dec 11 & the car appeared to be working normally. However, on dec19, while stopped at a red light, the car began to shake back & forth at idle & the rpms started to go up despite my foot being on the brakes. The car behind me saw what was happening & helped me pull over to the side of the road. I had the car towed to the dealership yet again. The dealership stated that they were able to duplicate the issue on dec 23, 2020. However, no fix was done to the car. The dealership claimed that the car was in a 'relearn' process & it would need more time for the car to 'relearn' how to drive again. Everything seemed okay after the dec 23 incident until feb 8 2021 when I tried to stop while in traffic & the brakes would not work at all. I narrowly avoided getting into a major accident & once again brought the car to the dealership. The dealership found that the master cylinder assembly was internally defective & was not holding pressure and as a result the brakes were not working. The vehicle was returned to me on feb 11 2021.