2020 Hyundai Sonata: check engine light

Filed Oct 15, 2026 · Brakes, Engine · KY

Vehicle experienced intermittent, severe powertrain defect resulting in a critical safety hazard. Between 30K and 36K miles, the vehicle underwent 3 violent highway deceleration episodes. During these events, the engine began shaking, escalating to violent shaking; with deceleration and coming to a stop, it would shake, then sputter as if it would die. Coming to a complete stop, a total stall was prevented only by the ECM forcing a limp mode lock at 1200 RPMs. When Auto Hold was engaged at this point and my foot was removed from the brake pedal, the mechanical surge caused the vehicle to unexpectedly lurch forward, fighting against and nearly overriding the factory Auto Hold braking safety feature before finally holding. Luckily, no pedestrian was walking in front of my car when this occurred. No check engine light (CEL) or dashboard warning ever illuminated. This safety compromise is directly tied to an ineffective or adjacent remedy involving Service Campaign 9B1 (Opcode 40D219R0) and Safety Recall 286. Under this Opcode, a factory software flash deleted the standard OBD-II trouble code P0451and substituted it with a manufacturer-specific shadow code P14EE00. This software manipulation suppressed universal emission/pressure sensor faults, masking a volatile physical defect within the high pressure fuel delivery and ignition systems. Dealer diagnostics on a running, compromised engine flagged an improper fuel injector pulse and subsequently a failing Cylinder 3 ignition coil. All four injectors were replaced but only one coil, leaving 3 non-updated , factory defective coils in the engine. The vehicle remains an ongoing highway stalling and brake-override hazard due to an incomplete field remedy of a recall-adjacent system. I've filed a Hyundai Complaint with assigned case number 43394228 regarding Safety Recall 286. (Two episodes of the attempted Auto Hold override occurred - first 09/09/2026 and second 09/29/2026.)

Filed Jul 10, 2026 · Electrical, Engine · AZ

My vehicle while driving, it is jerking and shaking. When I come to a stop, the cars rpms go up and down while the car is shaking. When I pressed the gas pedal to accelerate the car will not accelerate as normal and the car jerks as I’m driving it. The RPMs rev up and down without any pressure placed on the gas pedal. The check engine light came on.The miles per hour only allows me to put one digit. I wanted to clarify that the problem is occurring anywhere between 0 mph to 65 mph when these the car jerks and shakes and the RPMs go up and down without me pressure on the gas pedal.

Filed Jun 9, 2026 · Engine, Transmission · NC

For my vehicle the Check Engine light has been on continuously throughout the last 6 months and mechanics are going to have to replace the thermostat. Multiple auto mechanics have indicated online that this is a very common problem with many Hyundai vehicles from 2020-2023 and can be a danger due to temperature control not being accurate for vehicles (Code P2181). Many owners of these Hyundai vehicles have experienced this issue leading online and this issue should be made aware to Hyundai and the general public to see if this is something that needs to be made aware for the safety of drivers to determine if their vehicle is at an accurate temperature.

Filed May 8, 2026 · Engine, Fuel system · 80,000 miles · MD

The contact owns a 2020 Hyundai Sonata. The contact stated that the fuel failed to go into the tank. The seat failed to move. The engine light illuminated. The vehicle stalled. While driving, the fuel gauge went from full to empty. The contact received the federal safety agency Campaign Number: 25V796000 (Fuel System, Gasoline) after the failure. The vehicle was towed to the local where it was diagnosed that the fuel tank had expanded. The vehicle was repaired approximately eight months later. The contact called another local dealer. Ourisman Hyundai Bowie, 2404 Crain Hwy A, Bowie, MD 20716, who was unable to schedule an appointment. The manufacturer instructed the dealer to keep the vehicle due to it being a fire risk. The manufacturer was contacted regarding a buyback. The failure mileage was approximately 80,000.

Filed May 7, 2026 · Fuel system · 82,000 miles · CA

The contact owns a 2020 Hyundai Sonata. The contact stated that while driving at an undisclosed speed, the check engine warning light illuminated. The vehicle was taken to an independent mechanic, who retrieved a diagnostic trouble code for the check valve. The mechanic related the failure to the federal safety agency Campaign Number: 25V796000 (Fuel System, Gasoline), associated with the VIN; however, the contact had not received notification of the recall. The vehicle was then taken to the dealer, who determined that the check valve had failed and the fuel tank was deformed. The contact was referred to the manufacturer. The vehicle was not repaired. The manufacturer was made aware of the failure, and a case was filed. The manufacturer offered to buy back the vehicle, but the contact declined the offer. The failure mileage was approximately 82,000.

Filed Sep 10, 2025 · Engine, Transmission · 101,000 miles · MS

The contact owns a 2020 Hyundai Sonata. The contact stated that the vehicle hesitated while depressing the accelerator pedal, with the check engine warning light illuminated on the instrument panel. The vehicle was taken to several independent mechanics and dealers to be diagnosed; however, the cause of the failure was not determined. The contact stated that one mechanic replaced an unknown sensor, but the failure returned soon after the repair. The manufacturer was notified of the failure. The vehicle was not repaired. The failure mileage was approximately 101,000

Filed Aug 7, 2025 · Transmission · NY

My certified pre-owned 2020 Hyundai Sonata has experienced the same critical transmission failure three times since October 2024, creating dangerous safety conditions on highways and city streets. Component/System Failed: Transmission control system with consistent P0768 error code (Shift Solenoid D Circuit Fault). Safety Risks: The transmission failures cause sudden power loss and inability to accelerate while driving, including on highways at speed. This creates immediate danger to myself, passengers, and other drivers when the vehicle unexpectedly loses power during traffic situations requiring acceleration or merging. Problem Reproduction: The failure has been confirmed and reproduced by authorized Hyundai dealership three separate times: - [XXX]: P0768 error, replaced shift control solenoid valve - [XXX]: Same P0768 error returned, replaced entire transmission control unit - [XXX]: Same P0768 error again, replaced complete control wiring harness with extensive dashboard removal Warning Signs: Each failure was preceded by transmission hesitation, rough shifting, and check engine light activation before complete power loss occurred. Manufacturer Inspection: Hyundai technical assistance case #[XXX] was opened for the third failure, acknowledging the recurring nature of this defect despite multiple repair attempts. Assessment: This appears to be a systematic manufacturing defect in the transmission control system affecting safety. Despite three different repair approaches by Hyundai, the identical P0768 error continues to recur, suggesting a fundamental design or manufacturing flaw that creates ongoing safety risks for drivers. The vehicle was out of service for 44 total days across these three incidents, indicating the severity and complexity of this recurring safety defect. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Jul 31, 2025 · Engine, Fuel system · WA

Whille driving back to Washington state my car check engine light came on and the car shut off while I was driving. I had to have it towed to the nearest city whi ch was Laramie Wyoming. There is no Hyundai dealer had to drive the car once it started back up to Cheyenne Wyoming it was checked. My on star told me there was a problem DTC P0145100 the status had red triangle the DTC power system powertrain and the DTC sub system EMS. I was told and given paperwork by the dealer and was told the car would need major repairs and could take up to 21 days once the work started it would have to he completed there because Hyundai had campaign dealing with my cars problem. I was told I could drive the car home but if the check engine light is flashing pull over immediately. My car is now at the 3rd dealer when I took it to Korum in Puyallup they did not have anyone to diagnose the vehicle only update onboard computer. They said and documented nothing was wrong with the vehicle which is inaccurate. I told Korum about the paperwork from the dealer in Cheyenne they did not so much as look at it. I took the car to the Dealership in Auburn Washington they to had the same findings as Wyoming also there was additional findings which corresponded with the smell of gas and my tank going empty after filling and trying to fill tank because was showing low fuel warning. Pictures were taken of the gas tank which had expanded as well as other pictures of the findings. I was told in Wyoming and Auburn that the code and findings are consistent with the Hyundai campaign

Filed Jul 2, 2025 · Fuel system · LA

Something went wrong in the fuel tank that caused it to become so pressurized that the tank expanded up and out so far that it pushed the exhaust pipe down and my back seat of out place. The only issue I had was the car was accelerating slower than usual but it wasn’t even enough of a difference for someone who didn’t drive it every day to be able to tell. It did this for two days then the check engine light came on and it just read “powertrain”. Began slow acceleration on 06.08.2025. Check engine light came on the night of 06.09.2025. I took it to the dealership 06.10.2025. I immediately took it into the dealership and they told me the car could have exploded. There was a previous recall for the fuel pump that I had replaced at the dealership. After seeing my car, they said their techs and the techs at HMA have never seen one this bad and that maybe after replacing the recall part the system update failed in my vehicle and the issue was never actually resolved.

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 7, 2025 · Fuel system, Seats · NJ

My wife and son experienced a terrible situation on the way home from training. They had to stop at the nearest gas station due to the vehicle showing extremely low gas in the tank during a short drive home. The fuel gauge initially showed about half a tank but drastically dropped on the way home. They stopped at a gas station to add fuel but during the process, fuel starting spewing out of the tank. The vehicle was scheduled to be dropped off at a later date for an open recall (service campaign 9B1). I called the dealership and told them I needed to get the vehicle in right away due to the incident. After bringing the vehicle to hyundai, they told me that the fuel tank exploded causing the tank to swell all the way around. Because the tank is located under the rear seat, we constantly heard air coming in due to the rear seat not seating properly. The check engine also was on and we smelled fuel while driving the vehicle. Hyundai representatives has been avoiding my calls to the point where I had to go in person for an update. Apparently, a district manager had to come inspect the vehicle to advise the dealership how to write up the request to send to corporate.

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.