Hyundai Santa Fe hesitation problems

Filed Oct 15, 2026 · Electrical, Engine · CA

On [XXX], Laguna Niguel Hyundai performed Service Campaign 9C2 (ECU software update for Theta II emissions improvement, Hyundai TSB 26-01-013H) on my 2017 Hyundai Santa Fe Sport. Immediately after the update, the vehicle developed drivability problems that did not exist before: rough/harsh shifting, hesitation, and loss of power during cold-start operation (the first 1-3 minutes after engine start), plus intermittent infotainment and navigation system failures. Hyundai's own dealer notice dated 05/18/2026 acknowledges vehicles may exhibit 'hesitation or rough shifting' after the 9C2 update and states the matter is 'currently under review' — no permanent fix has been released. The dealership that performed the recall has since refused to service my vehicle again. I opened case #[XXX] with Hyundai corporate; my inquiries on 09/03/2026, 09/11/2026, and 09/17/2026 asking for a corrective action have gone unanswered. The hesitation and power loss are a safety hazard when merging into traffic or crossing intersections. I request the federal safety agency investigate this pattern. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Oct 13, 2026 · CA

On XXX, [XXX] Hyundai performed Service Campaign 9C2 (ECU software update for Theta II emissions improvement, Hyundai TSB 26-01-013H) on my 2017 Hyundai Santa Fe Sport. Immediately after the update, the vehicle developed drivability problems that did not exist before: rough/harsh shifting, hesitation, and loss of power during cold-start operation (the first 1-3 minutes after engine start), plus intermittent infotainment and navigation system failures. Hyundai's own dealer notice dated XXX acknowledges vehicles may exhibit 'hesitation or rough shifting' after the 9C2 update and states the matter is 'currently under review' — no permanent fix has been released. The dealership that performed the recall has since refused to service my vehicle again. I opened case #XXX with Hyundai corporate; my inquiries on XXX asking for a corrective action have gone unanswered. The hesitation and power loss are a safety hazard when merging into traffic or crossing intersections. I request the federal safety agency investigate this pattern. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 27, 2026 · Engine, Transmission · MD

Immediately following the mandatory Hyundai Servie Campaign Update 9C2-ECU THETA 11my vehicle began exhibiting severe hesitation, very rough idling, jerking at slow speeds and when gear changes, difficulty going up inclines and almost feel at times as though it is about to lose power which poses life threatening situations especially when turning into traffic. I have reported it to the dealers who never once test drove the vehicle but said to me that they did and could find no problem, however they did make me pay for repairs which never fixed the problem. I returned three times with the same issue. They recommended a Fuel Induction Service and a Auto Trans Service. Spark plug change. Igniton coils change. Nothing worked!

Filed Sep 23, 2026 · Engine, Transmission · TX

On 03/26/2026, my 2019 Hyundai Santa Fe received Hyundai Service Campaign 9C2 (TSB 26-01-013H-1), which included an Engine Control Module (ECM) software update for Theta II emissions improvement. The vehicle did not have the following drivability problem before this software update. Immediately after the 9C2 update, the vehicle began jerking/bucking slightly at low speeds, most noticeably around 10-20 mph when coasting with no accelerator input or when applying very light throttle. Acceleration response also feels slower than before the update, with noticeable hesitation when the accelerator is pressed. The problem is most noticeable during the beginning of a drive when the vehicle is cold. After driving for some time and the vehicle warms up, the symptoms improve, although the change in drivability remains noticeable compared with operation before the update. There have been no warning lights or warning messages associated with the problem. The issue began immediately following the ECM software update. The vehicle has not yet been returned to the dealer for diagnosis or confirmation and is available for inspection. I am concerned about the safety implications of delayed or unpredictable acceleration response, particularly when entering traffic, crossing an intersection, or merging when timely acceleration may be necessary. I am reporting this because the condition began only after Hyundai Service Campaign 9C2 was performed and I believe the federal safety agency should evaluate whether this ECM software update is causing similar drivability and acceleration problems in affected vehicles.

Filed Sep 19, 2026 · Engine, Fuel system · PA

Hyundai performed recall #9C2, on 7/2/26. Since that time, the engine has a full time miss. When it is cold, it will hesitate, kick and buck. Hyundai is aware of this. Their solution is to warm the car for 3 to 5 minuets before moving. What happens if there is an emergency and you can't wait? Possible accident with injuries trying to pull into, or cross traffic! I have filed a case with Hyundai, and they just update that they are aware and working on a solution with no expected date for the software fix. This is a serious problem, and they need to fix SOON! Also, when an engine runs like this, over a period of time it will destroy the catalytic converter. Who's going to pay for that??

Filed Sep 19, 2026 · Engine, Transmission · NJ

Service update 9C2. Car hesitates or slightly bucks on a cold start. No remedy to fix yet.

Filed Sep 9, 2026 · Acceleration, Engine · NE

Vehicle was brought to an authorized dealership for service, and while there Campaign 9C2 (ECU Software Update for Theta II Emissions Improvement) was performed. Immediately following this software update, the vehicle developed drivability degradation, specifically engine stutter/hesitation and rough transmission shifting during cold starts. When attempting to accelerate in the first few minutes of driving, the vehicle delays engagement and then suddenly surges or lurches forward unpredictably. This creates a safety hazard, as the unpredictable power delivery and lag prevent the vehicle from accelerating safely when merging into traffic or turning across oncoming lanes, placing occupants at an immediate risk of a collision. The software logic error is fully reproducible every time the vehicle has sat long enough to cool down. The dealership confirmed the update was applied. There were no warning lamps or symptoms prior to the 9C2 update; the failure was caused directly by the manufacturer's campaign software modification to the Engine Control Unit (ECU). The vehicle and its ECU are available for inspection upon request.

Filed Sep 7, 2026 · Fuel system · NY

My vehicle had a very strong gas smell inside and outside of the car. I found a gas puddle under the car coming from the back of the vehicle. Car was hesitating when I stepped on the gas. I was afraid it may stall. I drove the vehicle to my regular service station. Vehicle has an active fuel leak and this is a fire hazard. I was very concerned whether the vehicle would stall and cause an accident. Warranty coverage was denied.

Filed Sep 3, 2026 · Engine · NC

On May 26.2026, Southern States Hyundai performed mandated Service Campaign 9C2 (Theta II Emissions Improvement). The software immediately caused drivability degradation and a catalytic converter failure, mirroring the defects Hyundai acknowledged to the federal safety agency on May 18, 2026. Corporate customer care is using an unrelated oil consumption testing protocol to deflect liability and charge me $1,400 for the testing and/or $4002 for the catalytic converter out of pocket for damage caused by their own recall software. This hesitation is a severe safety risk when accelerating into traffic.

Filed Sep 3, 2026 · Engine, Transmission · 5,100 miles · OK

The contact owns a 2026 Hyundai Santa Fe. The contact stated that while driving at an undisclosed speed, the vehicle hesitated while accelerating. The failure occurred mostly while making a left turn and while accelerating from a stop and continued for 10-seconds before self-correcting. There was no warning light illuminated. The contact stated that there was almost a crash during the failure. The failure was not self-corrected after one failure. The vehicle was turned off and restarted, and the failure was then self-corrected. The vehicle was taken to the local dealer, who was unable to determine the cause of the failures, and there was no DTC found. The manufacturer was notified of the failure, but no assistance was provided. The failure mileage was 5,100.