2020 Hyundai Sonata transmission problems

Filed Sep 3, 2026 · Electrical, Transmission · TX

I am submitting a safety complaint regarding a recurring, unresolved electrical defect in my 2020 Hyundai Sonata SEL. The vehicle fails to recognize when the ignition is switched off, leaving core vehicle systems active and causing severe parasitic battery drain that leaves the car immobilized. ​Description of the Problem: ​False "On" Status: After parking, turning off the engine, and exiting the vehicle, the car continues to register as though the ignition is still active/on (accessories, cluster, or vehicle network remain awake). ​ Severe Parasitic Draw: Because the vehicle fails to shut down its electrical circuits, the 12-volt battery repeatedly discharges overnight or while parked for short durations. ​Battery Replacement Did Not Resolve Issue: The 12-volt battery was replaced with a brand-new unit to eliminate typical wear, yet the drain and false "on" behavior persisted immediately. ​ Frequency: The vehicle frequently fails to start, requiring constant jump-starts or roadside assistance to operate. ​Safety Hazard: This defect creates a direct safety risk by repeatedly stranding the driver without warning in public locations, traffic stops, or remote areas. In addition, an electrical system that fails to enter a sleep state creates a potential hazard for component overheating, failure of electronic security and locking systems, or total electrical failure while attempting to restart or operate auxiliary safety equipment. Other Hyundai owners have reported identical issues where the body control modules or ignition logic fail to power down. ​Corrective Action Requested: I request that the federal safety agency investigate this electrical shutdown defect across the 2020 Hyundai Sonata model year to identify whether a faulty Body Control Module (BCM), smart key receiver, or ignition switch relay requires a safety recall and software or hardware remediation. Battery replaced on 09/04/2026 Car inspected/diagnosed by Hyundai Dealership on 09/03/2026

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 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 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, 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 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 Mar 31, 2025 · Acceleration, Fuel system · OH

On or about November 13, 2024 our Hyundai Sonata 2020 gas tank almost exploded. We drove our vehicle to a dealership so that it could be checked because we kept hearing something that sounded like a loud pop / thumb underneath our vehicle. We had already been receiving notifications of a powertrain issue with the vehicle for years (without the dealership resolving the issue). So we were taking the vehicle in for numerous reasons when, the minute we drove our vehicle into the service bay (of a new and unrelated dealership) we were told that Hyundai's Corporate branch has ordered our vehicle grounded and told us we COULD NOT LEAVE with our vehicle or drive our vehicle off the dealership's lot. We were advised that our vehicle had almost exploded and that we were lucky to have brought the vehicle in. We were told that our vehicle should have never left the lot the day we purchased it brand new. We were told that our vehicle's backseats had detached and separated away from the frame of the vehicle. Our vehicle has been at the dealership since the day of the incident (e.g., on or about November 13, 2024). Our vehicle is still under factory warranty and powertrain warranty and Hyundai was not given us an end in sight or advised the public of the issue with their vehicles. WE were told that the vehicles needs repairs such as: 1. The vehicle needs the fuel tank assy and all of the parts for the tank, check valve, and campaign sticker: Please see TSB: 24-01-02OH

Filed Nov 22, 2024 · Electrical, Transmission · CA

I believe the transmission malfunctioned as I reached 60 MPH / 4000 RPMs on the highway when it suddenly did not want to accelerate past that. The more I stepped on the gas pedal, the more it slowed down. I attempted to use the paddle shifters to shift up or down, but I was unable to shift up and shifting down did not allow me to accelerate past 4000 RPMs. The flow of traffic was faster than I could keep up with, and not being able to accelerate made it unsafe to be on the highway. I had to pull over, and get off of the highway. I found that others have reported this same issue online with the same make/model/trim, but I have not had time to take it in to be looked at. No warning lamps, messages, or other symptoms prior to failure. I only noticed when I got on the highway and needed to reach speeds greater than 60 MPH. Turning the car off, waiting a bit, then starting it again seems to have resolved the issue, but I am still uneasy with this having happened so suddenly. I fear the issue may return in the future based on what I have read online. The car is available for inspection upon request.