2015 Hyundai Sonata: jerking or lurching

Filed Oct 1, 2026 · Engine · CT

"I am filing a complaint regarding severe vehicle jerking, engine surging, and rough transmission shifting immediately following the completion of Hyundai Service Campaign 9C2 (TSB 26-01-013H-1) on my 2015 Hyundai Sonata. The vehicle exhibits dangerous hesitation and lurching during cold starts. This behavior creates a traffic hazard when pulling out of driveways or into intersections during the first 3 minutes of operation. The manufacturer has acknowledged this cold-start defect in an internal 'Drivability Information' memo but has not provided a permanent remedy to repair the software logic."

Filed Sep 11, 2026 · Engine, Fuel system · VA

After receiving the Hyundai Service Campaign 9C2 update on my 2015 Hyundai Sonata on XXX, I have started having jerky acceleration when the car is first started and am driving. Also, while driving at highway speed (~65 mph)) and I take my foot off the accelerator to coast, the engine RPM drops suddenly, anywhere from 250 rpm to 750 rpm, then recovers abruptly to where it was at prior to the drop (typically around 2000 rpm). The engine rpm also drops while driving at slower speeds and recovers but is not as noticeable as it is at highway speeds. It was not doing this prior to the Service Campaign. There are no check engine lights or pending codes. I brought it back to the Hyundai dealer and discussed the issue with them on XXX. They acknowledged it was likely due to the Service Campaign and they did not want to keep the car to look at it and said no damage was being done and it was safe to drive. They said a fix was in the works but did not know how long until it was released and I should receive information in the mail on it. Video link [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Aug 6, 2026 · Electrical, Fuel system · MA

1.) Following Hyundai's 9C2 Campaign update for the ECU that was completed back on May 27th, 2026, my 2015 Sonata went into limp mode [solid check engine light present] while I was accelerating up an on-ramp on the 2nd drive cycle since the update was performed. I was already far away from the dealership so I was forced to limp it to my local shop that I regularly use to have it checked out. It was confirmed that the code on the vehicle was P200A for intake manifold runners. Since the update was for smog regulation, the code was cleared in order to see if it would come back. Since then, it has not, however the vehicle continues to have one persistent problem. The RPMs will dramatically dip and then surge back upwards while the car is coasting (no gas and no brake applied). 70% of the time, you can feel the car violently jerk as it appears to try and correct itself. 2.) I've brought this car to multiple dealerships, have a case open with corporate and have also found that this is a systemic issue with this specific update in these cars. All and all, nothing has been done. I'm repeatedly turned away over and over again because their techs are only permitted to look into it once they have hard evidence of a fault. In this case, that would be a dashboard light. I'm told that I may only return if the check engine light comes back, which as I mentioned previously, posed a HUGE safety risk to myself the first time it appeared. If I can only go 55mph down the highway, I am at risk of being rear-ended or struck in some way. 3.) The problem has not been reproduced by the dealer as they will not test drive it to see the dip and spike. However, the code was still pending for awhile in the vehicle before it cleared it on its own, so that was acknowledged by at least one place. 4.) Vehicle has not been inspected by anyone but a dealership and local mechanic. 5.) No other signs prior to the vehicle limping out on me other than some acceleration concerns on May 27th, 2026.

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 May 19, 2026 · Engine · CA

In August 2025, my car went into "limp mode" (go no faster than 40 MPH and it was lurching and speed dropping) on the freeway, which was scary and dangerous. Once home, I called a certified mechanic. When this mechanic tried to start the car, it made a terrible clacking noise. He told me it sounded like the main bearings were going out. He discovered that there was a recall on this particular vehicle because the main bearings would fail. The local dealer confirmed that the car was subject to the recall and requested that the car be brought in. Because I am on limited income, I could not afford to have the car towed until November 2025. Once there, the dealership verified that the main bearings went out. A claim was made to the manufacturer. The claim was denied claiming "outside influence." I provided service records to the manufacturer, but before they had all the maintenance records, they closed my case and will no longer take documents or even speak to me or the dealer. I have been without a car for almost 10 months. I have seen documented cases that trying to start the car could lead to dangerous engine fires.

Filed May 11, 2026 · Engine · 102,198 miles · IA

The contact's son owns a 2015 Hyundai Sonata. The contact stated that while the vehicle was being driven at 40-50 MPH, the vehicle began to jerk. The check engine light was illuminated. The vehicle was taken to an independent mechanic who determined the failure was related to the engine. The local dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 102,198.

Filed Oct 9, 2025 · FL

I am reporting a recurring and unresolved hybrid system failure in my 2015 Hyundai Sonata Hybrid Limited that poses an ongoing safety risk to me and my family. The issue involves a "Hybrid System Warning – Safely Stop and Do Not Drive" message that appears randomly while driving, causing the vehicle to jerking and creating dangerous conditions on the road. This issue first occurred in February 2024 and has persisted through October 2025 despite repeated service visits and costly out-of-pocket repairs. The hybrid battery was eventually replaced after 8+ months of delays, but the exact same warning and jerking symptoms returned in March 2025 and have never been properly resolved. The dealership (Crown Hyundai in St. Petersburg, FL) and Hyundai corporate case management have been unable to replicate or diagnose the problem consistently, and continue returning the vehicle to me in unsafe condition. On October 3, 2025, the same warning reappeared and the vehicle was dropped off again for yet another service attempt. Again on October 7, 2025, I was told to pick up my car, they could not replicate the issue and could not find a code to respond to. To date, I’ve paid $1,748.65 for a repair (air flappers) that did not solve the issue, and spent months without use of the vehicle, continuing to pay for insurance during that time. I believe this is a defective hybrid propulsion system that meets the threshold for investigation and possibly a recall, given the repeat safety risk and lack of resolution. Please investigate this matter for the safety of other drivers as well.

Filed May 12, 2025 · Acceleration, Brakes · IL · crash

My 2015 Hyundai Sonata has demonstrated multiple instances of unintended acceleration and braking failure: April 20, 2024 – While idling in a drive-thru line, the vehicle suddenly lurched forward without any attempt to accelerate and crashed into the vehicle in front of me. I was unable to stop it. This resulted in the other car being totaled. I took it to a Hyundai dealership afterward, but they found no definitive cause. April 4, 2025 – My daughter was driving and attempted to stop at a red light. Despite applying the brakes, the car did not stop and continued through the intersection, striking the door of another vehicle. May 12, 2025 – Today, while using cruise control set to 55 mph, the car began accelerating beyond the set speed without input. It appears the cruise control system is malfunctioning and not disengaging as expected. The vehicle currently shows no open recalls, but I found that similar issues were previously investigated under the federal safety agency action DP21003 for this model year. These incidents occurred months apart, but the behavior is consistent and extremely dangerous. I am requesting a formal investigation. The safety of my family and others on the road is at risk.

Filed Feb 27, 2025 · Engine · CA

On February 15, I was on my way heading back home driving in the freeway went my car randomly started jerking. I pull over to the side on the road pop the engine, did a visible check and i didn’t see anything. I went back on the road and it happened again, this time my check engine light came on and the car car started to knock very bad since then. I did a diagnostic scan and a code, P1326 came up saying that something is wrong with my knock sensor. Went and took it to a mechanic and I was told that my engine is gone and I need to replace it. Also that Hyundai has been having issues of the engine for a while.

Filed Nov 20, 2024 · Engine · 12,257 miles · CA

The contact owns a 2015 Hyundai Sonata. The contact stated while driving 35 MPH, the check engine warning light illuminated. The contact stated that the vehicle went into LIMP Mode, was jerking, and failed to exceed 45 MPH. The contact pulled over to the side of the road. The vehicle was towed to the dealer, where the engine knock sensor was replaced; however, the failure recurred while driving. The vehicle was driven to a nearby dealer, where it was determined that the engine needed to be replaced due to the connecting rod bearing failure. The dealer filed a claim with the manufacturer; however, the claim was denied. The dealer replaced the two engine knock sensors and the main fuel lines. Additionally, the fuel tank was drained; however, the failure persisted. The vehicle was driven to the dealer, where it was determined that the engine needed to be replaced due to connecting rod bearing failure. The dealer filed another claim with the manufacturer. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 12,257.

Filed Jul 4, 2024 · Brakes, Electrical · NC

At 40,000 miles the transmission is already jerking, shifting hard into gear and downshifting hard .

Filed Dec 30, 2023 · Engine, Fuel system · CA

The car has been having problems with oil consumption. The problem became known in 2022, but the dealer/service department (Frank Hyundai, National City, CA 91950) did not take care of the issue and did not care about safety. The dealer told me, "Your car is OK." On 7/3/2023, the engine light came on. A second round of oil consumption tests began along with a 90,000-mile service, including replacements of filter assy and gasket, four new tires and front and rear brakes, spark plugs, suspension/steering repair, shaft assy, engine repair, cooling system service, and fuel induction service. Shortly after, the car slows down even when my foot is on the accelerator. It feels as though the vehicle will stop. I can see the rpm gauge erratically going up and down. The car lurches or jerks. I reported the jerky problem to the dealer at the second 1000-mi oil consumption test, but the dealer did not make any diagnostic tests or repairs because, per the dealer, "it did not jerk while we test-drove it." The problem continues.