1,083 of the
22,259 complaints filed about the Hyundai Sonata
are about the transmission —
5% of everything owners reported.
The worst model year for it is 2011.
1,083
Complaints
5%
Share of all complaints
48
Crashes
18
Fires
Transmission & Drivetrain complaints by model year
The contact owns a 2025 Hyundai Sonata. The contact stated that while the accelerator was depressed, the vehicle hesitated, jerked, and failed to accelerate as intended. The failure occurred while driving from a stop and while driving at various speeds, causing the vehicle to decelerate during the failure. While depressing the brake pedal, there was a rubbing or grinding coming from the vehicle, and the braking was rough. There were no warning lights illuminated. The vehicle was taken to the dealer, who was unable to determine the cause of the failure. The vehicle was not repaired. The manufacturer was not made aware of the issue. The failure mileage was approximately 38,000.
NHTSA complaint #11757370 — an unverified report by a vehicle owner.
I recently had the 9C2 Emissions recall update performed on my car, and since the update my car drives like total garbage after a cold start. It hesitates to accelerate, it bucks when trying to accelerate, and it’s to the point the engine is about to stall. I took it back to the Hyundai dealership and they said they are aware of the issue, but there is no fix from Hyundai at this time. This is a major safety concern, as the car barely wants to accelerate after a cold start. Please have Hyundai fix this safety issue.
NHTSA complaint #11757253 — an unverified report by a vehicle owner.
I own a 2023 Hyundai Sonata SEL. Over approximately three years, the vehicle experienced four separate incidents involving sudden loss of engine power and recurring fuel injector/powertrain problems. Three of these incidents occurred while the vehicle was being driven on interstate highways, creating serious safety concerns. The first incident occurred on XXX, on [XXX] [XXX]. My daughter was driving the vehicle at the time when it suddenly lost power while traveling on the interstate. She had to maneuver the vehicle to the shoulder under unsafe traffic conditions. The second incident occurred on XXX, on [XXX] near [XXX]. I was driving the vehicle when it again experienced sudden loss of power while traveling at highway speed. The third incident occurred on XXX, in [XXX]. The vehicle experienced another significant power-loss event and required roadside assistance. The fourth incident occurred on XXX, on [XXX]. The vehicle again experienced a sudden loss of engine power while I was driving on the highway. Despite multiple repair attempts, including repairs related to the fuel injectors, the same or substantially similar power-loss problem continued to recur. Because the vehicle has repeatedly lost engine power while being driven, including multiple incidents at interstate highway speeds, I believe this recurring condition presents a serious safety risk. I am reporting these incidents so NHTSA can evaluate whether this may represent a broader safety-related defect affecting this vehicle model. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
NHTSA complaint #11755422 — an unverified report by a vehicle owner.
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.
NHTSA complaint #11749650 — an unverified report by a vehicle owner.
VEHICLE: 2015 Hyundai Sonata, 2.4L Theta II GDI engine Mileage at time of incident: [ 93k Date update performed: June 2026 Dealer/location where update was performed: Fitzgerald Hyundai Gaithersburg, MD DESCRIPTION OF PROBLEM: After my vehicle received the ECM software update issued under Hyundai Service Campaign 9C2 (ECU Software Update for Theta II Emissions Improvement, TSB 25-01-087H / 26-01-013H-1), the vehicle began exhibiting noticeable jerking/hesitation during acceleration that was not present before. For this vehicle this happens consistently after a cold start then does not happen again.
NHTSA complaint #11748280 — an unverified report by a vehicle owner.
My vehicle began experiencing excessive oil consumption several years before the engine failed. In approximately 2019, I reported the oil consumption to an authorized Hyundai dealership and expressed concern that my vehicle might have one of the known Theta II engine defects. I was told the Knock Sensor Detection System (KSDS) campaign had been completed and that my vehicle was not one requiring engine replacement. The excessive oil consumption continued. On June 6, 2026, the engine developed severe metal knocking, misfires, and became unsafe to operate. I was concerned the engine could fail completely or lose power while driving, creating a safety hazard for myself and others. The vehicle had to be towed to a Hyundai dealership on June 7, 2026. Hyundai of Kennesaw inspected the vehicle and verbally advised that the engine failure was caused by connecting rod bearing failure. Although the dealership identified connecting rod bearing failure, Hyundai Motor America declined to replace the engine and instead advised that it would not proceed with repairs because of the settlement provisions related to the vehicle's age and mileage. As a result, the vehicle remains inoperable. I am submitting this report because I believe this engine failure presents a significant safety concern due to the potential for sudden engine failure or loss of power while driving. I am also concerned that I reported symptoms years before the failure, yet the engine ultimately failed from the same type of defect associated with many Hyundai Theta II engines.
NHTSA complaint #11747939 — an unverified report by a vehicle owner.
The incident began following a routine maintenance visit on March 16, 2026, and has been a continuous, ongoing safety hazard every single day since. While the vehicle was in for routine brake service and an oil change, the dealership automatically applied an open, manufacturer-mandated ECU S/W Update THETA II (26-01-013H-1) under Service Campaign 9C2 Emissions (Code NP001-SC9C2) without my prior knowledge of its drivability side effects. This software flash directly compromised the vehicle's powertrain logic, creating two notable, daily safety failures. First, within the first 5 minutes of engine startup, and most pronounced on every cold engine startup, the throttle delivery is highly erratic, causing uncommanded low-speed surging. In a specific incident in a parking lot following a cold start, I accelerated to approximately 15 MPH and completely removed my foot from the accelerator pedal to coast. Instead of slowing down, the vehicle unexpectedly lunged and pulled ahead forcefully against my intent. Second, even after reaching full operating temperature, the vehicle completely loses safe and predictable engine braking at greater speeds; when lifting off the gas pedal, engine RPMs aggressively drop, causing the vehicle to coast freely as if in neutral. Re-applying the accelerator causes a violent "phantom shifting" downshift and a hard transmission lockup. My safety and the safety of others are put at risk every time the vehicle is driven. The low-speed throttle surging creates an ongoing risk of hitting pedestrians or cross-traffic, while the permanent loss of predictable engine braking drastically extends stopping distances. No warning lamps or diagnostic trouble codes (DTCs) appeared prior to or during these continuous failures. The vehicle remains available for inspection.
NHTSA complaint #11746404 — an unverified report by a vehicle owner.
My 2017 Hyundai Sonata SE, equipped with the Theta II 2.4L GDI engine, is experiencing severe powertrain failures including rhythmic metallic engine knocking, catastrophic oil consumption, and un-commanded surges/jumping in speed while driving. These symptoms manifested following an unauthorized engine replacement performed by Hyundai of El Cajon under Repair Order [XXX], where the dealer covertly outsourced my vehicle to a third-party shop (Legacy Motor Works) to install an unverified used salvage engine block rather than a certified factory assembly. This vehicle is a Class Vehicle under In re: Hyundai and Kia Engine Litigation (Case No. [XXX]), and the KSDS software update (Campaign 953) was successfully completed on my vehicle in 2019. The engine knock, surging, and oil consumption are consistent with the known connecting rod bearing failure defect described in NHTSA investigation PE17-007. The dealership is currently denying warranty coverage, citing a mileage limit that does not exist under my Lifetime Powertrain Warranty, and they are withholding physical documentation of the repair terms. The vehicle is also experiencing secondary safety failures, including a continuous airbag SRS warning light (two years) and electrical shorts caused by the salvage-yard alternator installation, which have destroyed 4 to 5 car batteries. This engine failure represents a significant safety hazard, as the vehicle periodically loses power and surges without driver input. I am requesting that NHTSA investigate this pattern of warranty denial, parts-sourcing fraud, and the safety risks posed by this substandard engine installation. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
NHTSA complaint #11745609 — an unverified report by a vehicle owner.
2019 Hyundai Sonata Sport. (Original owner). Problem: Transmission. [XXX] (9,912 miles). Lack of power, vehicle did not move when trying to merge onto freeway. Very unsafe. Also, hesitation and jerking. [XXX] (10,619 miles). Lack of power, hesitation, jerking. Hyundai tech performed TSB, TCU updates, ECU update for knock sensor performance, reset engine & transmission updates. [XXX] (41,332 miles). Harsh shifts, hesitation, jerking, clunk sound, gear grabs, bursts of power, lack of power. Unsafe to drive. February 2, 2026 (41,751 miles). Hyundai tech found leak at case seal. Hyundai replaced transmission. [XXX] rough start, vibration in pedals. March 9, 2026 Hyundai tech found transmission fluid leak at case seal. Hyundai replaced transmission. March 25, 2026 Hyundai service advisor voicemail said, have to submit to Hyundai another transmission replacement because new transmission is not good. Issues shifting in reverse, hard slams, loses gears. [XXX] picked up vehicle from Hyundai service dept. Harsh shifting, hesitation, jerking, clunk sound, gear grabs, bursts of power. Clunk sound in steering wheel when turned back-and-forth. Front end vibration & wobbly. Vehicle unsafe. May 26, 2026. I notified Hyundai Motor America. Case #[XXX]. June 10, 2026 (43,000 miles). Hyundai service dept. informed me of right and left front axle replacement, universal steering joint replacement. Vehicle unsafe. [XXX] (43,000 miles). Test drove car with Hyundai tech. Verified front end vibration & shaking. Vehicle unsafe to drive. Hyundai service manager said that Hyundai should recall the transmissions. To date, my car is still at Hyundai service dept. Hyundai's service manager said that the Hyundai service dept. will have a meeting regarding my car and include Hyundai's service director, etc. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
NHTSA complaint #11745802 — an unverified report by a vehicle owner.
Knock sensor needs to be replaced upon evaluation of an inspection on March 27, 2026. It failed a mission codes and upon my understanding the knock sensor one circuit range performance pink wonder single sensor is an engine failure as well as I did an ODB test myself on May 19 of 2026 for the Knox sensor as well and the check engine dominator reading at 2111 the the code indicated that bank one Knox and electrical circuit was out of it upper range or had it perform problem for a predetermined period of time and the code is P0326 and the secondary DTC is a combustion vibration sensor a circuit range performance which affects the powertrain. Also, I have switches with the electrical features in the vehicle as far as the ABS and the steering wheel controls and glitching for the cigarette adapter and plug-in area as well on top of the rear passenger side window, having issues with going up and down.
NHTSA complaint #11744374 — an unverified report by a vehicle owner.
Check engine light solid/engine failure while driving. 2018 Sonata SE purchased new in fall 2018. Around 50,000 miles started noticing oil level drop and had to add more before next scheduled change. Dealership service center said I just had to shorten the mileage between changes which didn't seem appropriate for a vehicle with 50,000 miles but I did. Continued to have oil consumption problem with no signs of leak, no burning oil smell or exhaust issues. Dashboard display would go off and when I immediately checked dipstick there was barely any oil so I'd add more then go in for full change. At 67,000 or so miles in June 2026, without oil display going off the engine light was now solid. Got to reputable service center near my home and oil was under a quart left yet the warning lamp hadn't gone off. They ran the engine error code P0304 and was misfire #4 cylinder and after compression test, #3 was very low and #4 very high. NOT drivable at that point then towed to dealership so yes, available for inspection by NHTSA at the dealership. For now they claim a 'tune up' is needed for spark plug replacement, valve cover gasket replace and fuel induction service that's my cost to incur which seems to just be fixing the damage of an engine oil consumption problem not fixing the issue that caused the damage. The engine seized/stalled without warning while I was driving the vehicle (granted at low speed in my neighborhood when the engine light turned on). I would not say the engine warning lamp occurred prior to the engine fail, it happed at the same time. This should not happen for a vehicle with my mileage and regular maintenance. I looked up NHTSA for potential recall or other helpful information and started to see extremely similar scenarios to mine and wanted to add complaint as well. This is getting very expensive outside of whatever cost the dealer wants as a fix with rental car needed and tow services. Thank you for your consideration of this engine safety issue.
NHTSA complaint #11744559 — an unverified report by a vehicle owner.
The contact owns a 2023 Hyundai Sonata. The contact stated that while driving at an undisclosed speed, the transmission shifted into neutral(N) and failed to shift into park or drive on three occasions. The vehicle was restarted. After restarting the vehicle, the vehicle was shifted into drive, and the contact continued driving. The message that the vehicle could not be shifted into other gears was displayed. The vehicle was originally purchased in another state. The vehicle was taken to the local dealer to be diagnosed. The dealer determined that the battery and fuel injector pump needed to be replaced. The vehicle was repaired; however, the failure recurred. The manufacturer was not contacted regarding the failure. The failure mileage was approximately 50.
NHTSA complaint #11744098 — an unverified report by a vehicle owner.
Following completion of Service Campaign 9C2 (ECU software update, TSB 25-01-087H) at a Hyundai dealership, my 2018 Sonata immediately exhibited drivability changes that were not present before the service. Symptoms include altered shift timing, hesitation, and rougher throttle response — particularly noticeable during the first several minutes of driving. These symptoms began on the first drive after the recall update was applied and have been consistent since. The vehicle was returned to the dealership for inspection. No underlying mechanical issue was found, confirming the drivability change is directly attributable to the ECU software update. The vehicle has been maintained strictly per Hyundai's manufacturer-recommended schedule and had no prior drivability issues. I am aware that numerous other owners of Theta II-equipped vehicles (Sonata, Santa Fe, Tucson) have reported identical symptoms following 9C2. At least one dealership has reportedly acknowledged this as a known post-update issue that Hyundai is working to resolve. The altered throttle and shift behavior poses a safety concern, as unexpected hesitation during acceleration affects predictable vehicle control in traffic. The vehicle is available for inspection upon request.
NHTSA complaint #11743622 — an unverified report by a vehicle owner.
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.
NHTSA complaint #11742918 — an unverified report by a vehicle owner.
[XXX] [XXX] [XXX]; [XXX] [XXX] [XXX] Date: XXX To: National Highway Traffic Safety Administration Office of Defects Investigation (ODI) Subject: Formal Safety Defect Complaint – 2017 Hyundai Sonata Theta II Engine Failure, Excessive Oil Consumption, Intake/Engine Component Failure and Safety Hazard Dear Sir or Madam: I am submitting this formal complaint and request for immediate investigation into the dangerous and ongoing mechanical failures involving my 2017 Hyundai Sonata equipped with the Theta II engine. I believe this vehicle contains a serious manufacturing and/or engineering defect that presents a substantial safety hazard to consumers. My vehicle has experienced a pattern of progressive mechanical failure beginning with abnormal and excessive oil consumption, which appears to be directly associated with malfunctioning engine airflow and intake-related components. Specifically, the lower engine airflow system and intake functionality appear defective, placing excessive strain on the intake manifold system and contributing to cascading engine failures. As a result of these failures, the vehicle has experienced: Severe and excessive oil burning/consumption Intake manifold malfunction and abnormal operating stress Suspected overheating and/or premature head gasket failure Ignition coil failure and electrical shorting/misfires Progressive engine deterioration rendering the vehicle unsafe and unreliable Increased risk of sudden engine shutdown, stalling, fire hazard, or catastrophic engine failure while operating The vehicle has become increasingly unreliable and inoperable due to these conditions. These failures raise significant concerns regarding public safety, especially given the known history of complaints and recalls associated with Hyundai Theta II engine defects. I am deeply concerned that this vehicle may reflect a broader pattern of defective manufacturing, insufficient quality control. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
NHTSA complaint #11742419 — an unverified report by a vehicle owner.
To Whom It May Concern: I am submitting this complaint to report ongoing safety concerns involving my 2013 Hyundai Sonata. I purchased this vehicle in 2022 through financing and paid it off in 2025. Since acquiring the vehicle, I have experienced persistent mechanical issues that I believe may pose a safety risk to myself, my child, and others on the road. The most concerning issue involves the braking system. I have had the brakes replaced and serviced multiple times, yet the brakes begin grinding again within a very short period, including an instance where the grinding returned approximately one month after replacement. Despite spending money on repairs, the problem continues to reoccur. I am concerned that there may be an underlying defect affecting the braking system that is not being properly identified or corrected through normal maintenance. In addition, the vehicle consumes an excessive amount of oil, requiring frequent monitoring and replacement between oil changes. I am concerned that this issue could potentially lead to engine failure or other dangerous mechanical problems while the vehicle is being operated. As a single mother, I rely on this vehicle daily for transportation to and from work and for caring for my family. I have experienced significant financial hardship attempting to keep the vehicle operational and safe. Despite my efforts to maintain the vehicle, these issues continue to occur. I respectfully request that the National Highway Traffic Safety Administration review this complaint and determine whether these issues may be related to known defects, recalls, investigations, or patterns reported by other owners of 2013 Hyundai Sonata vehicles. I am willing to provide maintenance records, repair invoices, mileage information, and any additional documentation that may assist in evaluating this matter. Thank you for your attention to this complaint and for your commitment to vehicle safety.
NHTSA complaint #11742339 — an unverified report by a vehicle owner.
Went from 65 and dropped down to 40 going up grades on the freeway. Started shaking, check engine light went on and electric battery disappeared from dash. Got to top of grade, went back to normal. Problem repeated on next grades. Car had just left dealership lot an hour prior where it was safety inspected and they said all was fine. Took back to dealership for inspection and they said that there were no codes showing for what happened and all was well with the vehicle, when obviously it was not.
NHTSA complaint #11741506 — an unverified report by a vehicle owner.