2017 Hyundai Santa Fe: hesitation when accelerating

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 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 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 Aug 31, 2026 · Electrical, Engine · NC

Cold-Start Hesitation & Rough Shifting: Following the 9C2 ECU update, my vehicle is experiencing a brief period of throttle hesitation, rough shifting, or jerky transmission behavior specifically during cold-start operations.

Filed Aug 24, 2026 · Electrical, Engine · NJ

My 2017 Hyundai Santa Fe, purchased new from Lynnes Hyundai in February 2017, has approximately 93,000 miles. The vehicle previously developed a significant oil-consumption/engine problem that was diagnosed by Hyundai, and Hyundai replaced the engine with a remanufactured engine. Approximately two weeks after the engine replacement, the check-engine light illuminated and DTC P1326 was identified. The dealership replaced the knock sensor. Approximately two weeks later, the check-engine light illuminated again with a recurring P1326 condition. The vehicle is currently at Lynnes Hyundai and has been there approximately three weeks while they attempt to determine the cause. Hyundai Techline is involved. Prior to the current repair visit, while traveling approximately 60 mph, the vehicle experienced a very forceful hesitation that jerked the vehicle. I immediately slowed down and pulled onto the shoulder. The vehicle continued to hesitate intermittently while I drove slowly to safety. I was concerned that the vehicle could lose power or shut down while I was driving at highway speed, creating a risk of a crash. The recurring P1326 condition has been confirmed by the Hyundai dealership. The vehicle and engine have been inspected by Hyundai/Lynnes Hyundai multiple times, including after the engine replacement. The current recurring condition has not been resolved. The check-engine light is the warning lamp associated with the current condition. I do not know the underlying cause of the recurring P1326 condition; Hyundai is currently attempting to diagnose it. The vehicle is currently available for inspection at Lynnes Hyundai.

Filed Aug 21, 2026 · Engine · SC

After the update earlier this summer for an emissions issue, my car, a 2017 Hyundi Santa Fe Sport, has not run right. When it is cold, the first trip on the day, it hesitates and sputters to an extent that it is not safe on the nearest highway where the speed limit is 35. We have been compensating by driving slowly around the neighborhood for a few minutes, and then it's fine. It has been happening since the update of service campaign 9C2, the "Theta II Emissions Logic Improvement" recall. The local Hyundai dealer has been unable to provide a fix. We just picked it back up today, 8/21/26, after deciding against their latest idea, a fuel injector treatment for $200. Based on other examples I've read with similar or identical issues after the recall software update, I have concluded this is a safety issue that Hyundai must resolve.

Filed Aug 10, 2026 · Transmission · 63,036 miles · FL

The contact owns a 2017 Hyundai Santa Fe. The contact stated that while reversing, the vehicle jerked and shuddered abnormally. Additionally, the transmission hesitated, and the vehicle almost stalled. No warning lights were illuminated. The vehicle was taken back to the dealer where the contact was informed that the Service Campaign Number: 9C2 was completed. The contact was informed that the updated software was confusing the transmission and had caused the failure. The contact was informed that the remedy was not yet determined. In addition, the contact was informed that the dealer was waiting on instructions from the manufacturer. The vehicle was not repaired. The manufacturer was made aware of the failure but provided no assistance. The failure mileage was approximately 63,036.

Filed Jul 27, 2026 · Acceleration, Engine · VA

The 9C2 campaign software update introduced dangerous vehicle hesitation and unpredictable gear changes in active traffic, presenting and immediate crash hazard