2017 Hyundai Sonata transmission problems

Filed Oct 12, 2026 · Transmission · GA

I had my engine replaced under the Theta Engine lawsuit and I was due for the 9C2 service campaign and it was installed...ever since I picked up my car it shifts weird between 1st and 2nd. I brought it back to a different Hyundai dealer as the warranty work was done at another location and they recommended a transmission flush and relearn. They can feel it slipping and the other dealership noted no problems, which leads me to believe it was because of the service campaign. I also called corporate and the customer service rep had heard of this before as well as a bunch of forums online.

Filed Jun 22, 2026 · Electrical, Engine · CA

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 the federal safety agency 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 the federal safety agency 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)

Filed Jun 6, 2026 · Engine, Suspension · PA

[XXX] [XXX] [XXX]; [XXX] [XXX] [XXX] Date: XXX To: the federal safety agency 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)

Filed Jan 19, 2026 · Engine, Transmission · VA

My vehicle has a documented excessive oil‑consumption defect. After a 1,000‑mile oil‑consumption test performed by a Hyundai dealership, the engine was found to have consumed 2.8 quarts of oil, which is far above normal and poses a safety risk. The dealer referenced TSB 23‑EM‑008H and recommended a chamber cleaning but could not guarantee it would resolve the issue. Hyundai Motor America declined to cover the repair and refused to escalate my case. This level of oil consumption is consistent with known Theta II engine defects that have led to engine seizure, stalling, and fire in other vehicles. I am reporting this as a safety concern due to the risk of sudden engine failure while driving.

Filed Jan 3, 2026 · Airbags, Driver assistance · PA · crash

Airbags did not deploy no indicator light came on before nor after I was struck from my driver side front area and yes it is available for inspection upon request. My safety along with my sisters safety was put at risk due to the negligence and cheapness of the dealership I purchased the car from also from there misleading information and improper inspection before selling me the car Car has not been reproduced or confirmed The car was inspected by a third party appraisal company for damages amounts There were no lights on at all before the accident and I am pretty certain that the dealership cleaared the codes before selling me the car

Filed Nov 29, 2025 · Electrical, Engine · TX

e vehicle is burning approximately 2 quarts of oil every month with no external leaks. This indicates severe internal oil consumption, which is a known defect in Hyundai’s Theta II 2.4 GDI engines. I discovered oil inside the VVT solenoid electrical connector and on other wiring, which shows oil is traveling through the engine harness. This causes hesitation, rough running, and the risk of sudden engine power loss. The vehicle feels unsafe to drive because the oil level drops quickly, and the engine could seize or stall while driving. Hyundai vehicles of this generation have a history of excessive oil consumption, piston ring failures, and engine fires, and I believe my vehicle is experiencing the same defect. This is a serious safety concern.

Filed Sep 11, 2025 · Engine, Transmission · NV

What component or system failed or malfunctioned, and is it available for inspection upon request? The engine in my 2017 Hyundai Sonata Sport is defective. Oil pressure failed testing, oil contamination was found on the oil pressure sensor and connector, and the vehicle has experienced excessive oil issues. The engine is still in my possession and available for inspection upon request. How was your safety or the safety of others put at risk? The vehicle has gone into limp mode on the highway, which caused a sudden loss of power and created a dangerous situation in traffic. The car also shakes, misfires, and loses power unexpectedly, which could lead to stalling or loss of control at highway speeds. I do not feel safe driving the car. Has the problem been reproduced or confirmed by a dealer or independent service center? Yes. Multiple Hyundai dealerships have inspected the car. One confirmed low oil pressure and oil contamination at the sensor. Previous visits dismissed the oil warning and charged me for oil replacement instead of identifying the underlying defect. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others? Yes. The vehicle has been inspected by Hyundai dealers multiple times. I also have two inspection reports from the same dealer just two weeks apart with contradictory findings the first showing no oil issue, the second confirming oil contamination and failed oil pressure. Were there any warning lamps, messages or other symptoms of the problem prior to the failure, and when did they first appear? Yes. The oil warning light and check engine light have both come on. The vehicle has gone into limp mode, and symptoms have included shaking, misfiring, rough idling, and loss of power. These issues began months ago and have continued despite repeated service visits.

Filed Aug 23, 2025 · Transmission · IN

While driving about 45 miles per hour the gas engine shut off and the electric engine lost power, were able to coast a few miles under low power under electric engine and then engine shutdown completely and would not start, had car tolled to nearest mechanic, he confirmed eninge damaged by rod bearing failure, he tried to get a new engine to replace the damaged one and hyundai told him they could not sell him and engine

Filed Aug 5, 2025 · Acceleration, Engine · MI

I am leasing a 2017 Hyundai Sonata from Car City in Michigan. In May 2025, the vehicle received a brand-new engine replacement due to previous problems. I picked the car up on [XXX], and on the same day, the vehicle began malfunctioning. It would not accelerate properly, jerked and stalled, and multiple warning lights — including the check engine light — came on immediately. This made the car unsafe to drive. I contacted the dealer, but they told me to wait until Monday to get it looked at, leaving me with a dangerous and unreliable car. The vehicle had already been in the shop for over two months for the engine issue, and I had only driven it for six months beforehand. I believe the repair or replacement engine is defective or was not properly installed. This creates a serious safety hazard. A car that stalls while driving puts everyone at risk. I am filing this complaint so this issue can be investigated and addressed if others are affected. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Aug 4, 2025 · Engine, Transmission · TX

The engine in my 2017 Hyundai Sonata has been burning excessive amounts of engine oil over an extended period. The issue started approximately 10,000 miles ago but has worsened recently, requiring frequent oil top-offs between regular oil changes. The oil consumption is abnormal and not consistent with normal wear. This excessive oil burning poses a potential safety risk, including possible engine failure, stalling, or fire hazard due to low oil levels if not monitored carefully. The vehicle has not yet experienced a complete failure but the risk concerns me. The problem has been observed consistently during normal driving conditions. I have not yet had an official inspection or oil consumption test performed by a dealer, but I intend to request one. There have been no warning lights related to the oil burning issue, but the oil level drops rapidly and noticeably.