2015 Hyundai Sonata transmission problems

Filed Oct 11, 2026 · Engine, Fuel system · TX

I am filing this complaint regarding transmission and drivability problems with my 2015 Hyundai Sonata 2.4L following Hyundai Campaign 9C-2. My vehicle was running and driving perfectly before this update. I have always maintained it on time, followed proper maintenance schedules, and have records documenting its maintenance history. I never experienced these transmission issues before the update. The problems began immediately after the campaign was performed. In fact, I noticed the abnormal shifting before I even left the dealership after picking up my vehicle. Since the update, the vehicle has experienced poor and abnormal shifting behavior. I contacted the dealership to report the problem and also filed a complaint directly with Hyundai Corporate. I was told that Hyundai is aware of the issue, yet my complaint remains unresolved. I also located a document online indicating that Hyundai is aware of this problem. Additionally, I have seen numerous reports from other Hyundai owners describing similar transmission problems after receiving this same update. My vehicle has approximately 82,000 miles. The engine was replaced approximately one year before this complaint. Given the vehicle's excellent operation before the update, my documented maintenance history, and the immediate onset of the problems at the dealership, I am seriously concerned that Campaign 9C-2 caused or contributed to these transmission issues. I am requesting that the federal safety agency investigate whether this software update causes or worsens transmission shifting problems in affected Hyundai vehicles. Hyundai's awareness of the reported issue and the apparent number of similar owner complaints make this especially concerning. I believe this issue deserves investigation to determine its cause, assess any potential safety risks, and establish whether corrective action

Filed Sep 10, 2026 · Engine, Transmission · VA

In March 2026 Hyundai did an emissions update Campaign 9C2. Since that update my 2015 Hyundai Sonata SE has run rough and shifted hard. Hyundai stopped doing the update in May 2026. Hyundai has not provided any update to fix the problem they created. I am worried the update is damaging the motor and transmission of a car that was running just fine prior to the update.

Filed Jul 4, 2026 · Transmission · MD

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.

Filed Jun 25, 2026 · Engine, Transmission · GA

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.

Filed May 11, 2026 · Transmission · MO

Car stopped in the middle of the road , with warning beeps and warning messages on the dashboard saying "Check Charging System" .Engine was still running but even though I did accelerate - car did not move . I put on the emergency lights and turned off the car . Turned on the car few seconds later and was able to drive then but the check engine light was on. Slowly drove back to the home as I was less than a mile from the home. It happened on a local road with speed limit of 35 MPH and thankfully vehicles behind me stopped until I pulled over. Me and and 7 year old kid was in the car at the time of this incident

Filed Mar 24, 2026 · Engine, Transmission · MD

The bearing failure from the metal debris had been progressing silently for a long time. You can’t feel or hear it happening gradually. Then at some point the damage crosses a threshold where: ∙The oil can no longer circulate properly ∙The crankshaft bearings completely fail ∙Internal metal parts make contact with each other ∙Everything locks up instantly

Filed Feb 17, 2026 · Engine, Fuel system · SC

Component/System Failed: Engine – connecting rod bearing failure consistent with Hyundai Theta II engine defect subject to federal recalls and Consent Orders. The vehicle previously received Recall Campaign 953 (KSDS software update), intended to detect premature rod bearing wear. The engine is currently knocking and has been diagnosed as requiring replacement. The vehicle and engine are available for inspection upon request. Safety Risk: Rod bearing failure can cause sudden engine seizure or stall while driving, creating a significant crash risk due to loss of power steering and braking assist. Engine failure DID occurr despite prior recall software update, indicating potential recall remedy ineffectiveness. Sudden stalling in traffic placed myself and others at risk of collision. Dealer Confirmation: Hyundai of North Charleston confirmed through warranty history a prior engine replacement request (PA) was submitted by a previous owner but denied. The recall repair was never performed. Current diagnostic findings indicate engine failure consistent with known recall defect. However, Hyundai has refused to perform further inspection or goodwill repair solely due to the vehicle’s salvage branding. Inspection History: The vehicle has been inspected by a Hyundai dealership. No engine replacement was completed. Hyundai Customer Care has updated case notes but is declining remedy based on title status rather than mechanical condition. Warning Lamps/Symptoms: The vehicle previously received KSDS software update. Engine knocking developed consistent with rod bearing wear. The software did not provide effective prevention of engine failure. The engine now requires replacement. Hyundai is refusing recall-related remedy due to salvage title (predates my wonder ship by many years), despite federal recall obligations applying to the vehicle VIN. This complaint concerns potential failure of recall remedy effectiveness and denial of defect-related inspection.

Filed Nov 24, 2025 · Transmission · NY

The engine/powertrain on my 2015 Hyundai Sonata (VIN: [XXX] ) has failed due to extremely low compression in all four cylinders, causing severe misfires, hard starting, loss of power, and intermittent rattling noises, and the vehicle is currently available for inspection at the Hyundai dealership. This failure created a safety risk because the engine hesitates, struggles to start, and can stall or lose power during driving, which could lead to a loss of control or an inability to accelerate in traffic. The problem has been confirmed by both an independent mechanic and the Hyundai dealership, who documented low compression across all cylinders. The vehicle has been fully inspected by the dealership on Hyundai’s behalf after I opened a case with the manufacturer. Prior to the complete failure, the car showed warning symptoms such as repeated cylinder 4 misfires, rough starting, reduced power, rattling noises on startup, and the check engine light appearing several times beginning earlier this year. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Jun 26, 2025 · Engine, Transmission · IA

Our 2015 Sonata has experiencing Engine failure several times due to excessive and irregular oil consumption. Our family’s safety and the safety of others on the roadway were put at risk as the engine slows, shudders and stalls without prior warning and the check engine light does not come on until the vehicle slows and stalls. The vehicle was inspected at a local Hyundai dealership, and they indicated that this is not covered under warranty. Summary of Engine Issues and Failures: 1.May 3, 2022 – 68,671 miles (local Hyundai dealer) Check engine light on, shudder; oil change performed. No cause identified. Paid out-of-pocket. 2.August 23, 2022 – 75,527 miles (retail shop) Car engines failed on highway, towed to service shop. Valve cover gaskets replaced. Paid out-of-pocket in part and extended warranty paid part of the invoice. 3.April 29, 2024 – 109,229 miles (local Hyundai dealer) Excessive oil consumption noted; valve cover gasket replaced again. Paid out-of-pocket. 4.January 22, 2025 – 118,341 miles (local Hyundai dealer) Vehicle stalled en route to airport, towed to dealership; dealership advised oil change. Paid out-of-pocket. 5.May 20, 2025 – 122,000 miles (local Hyundai dealer) Engine codes P0300, P0302, P0303 identified. Dealer diagnosed excessive oil consumption likely due to ring wear or sticking rings, contributing to spark plug misfires. Recommendation: Engine replacement. Despite consistent and timely service, including multiple visits to the Hyundai dealership, the root issue has not been properly addressed. The current diagnosis of internal engine failure is a clear continuation of a pattern of unresolved engine problems (stalling in motion, oil leaks and oil consumption) all of which originated well within Hyundai’s original warranty. The vehicle has been well maintained, and all recalls have been addressed in a timely manner. Hyundai’s failure to acknowledge and take responsibility for this widely documented engine issue is a safety concern.

Filed Mar 24, 2025 · Transmission · MA

While traveling on local roads and highways the vehicle transmission randomly down-shifts one or two gears. This has occurred when traveling in any gear from gears 3 through 6. It probably doesn't happen in 2nd gear because that is a transitory gear and not a cruising gear. After quickly moving the shifter from automatic mode into manual mode and then back into automatic mode the transmission returns to the proper gear. However sometimes it has down shifted again in as little as 30 to 60 seconds after resetting the shifter. This has been happening for years. The dealership has been unable to fix it. Because it is random, the issue is not readily reproducible by the repair shop. Sometimes it has happened several times within a 15 minute period. Sometimes it has occured multiple consecutive days. Other times a week or two has passed with no incident.