2017 Hyundai Santa Fe power train problems

“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 NHTSA investigate this pattern.”

“Was driving down road car went into limp mode about caused a big wreck, check engine was flashing and heard a loud noise as I was trying to get to safety. Had the car scanned and was for code p1326 and looking at all the recalls nothing is for the 2.4l but y'all have been having a lot of issues with these theta 2 engines.”

“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!”

“Component/System Failed: Engine assembly (Theta II 2.4L GDI) and Exhaust/Catalytic Converter. Description: The vehicle suffered a failure associated with the known Theta II engine defects. Engine oil consumption and internal engine wear directly led to unburned fuel and debris entering the exhaust stream, resulting in severe catalytic converter restriction/failure. Safety Risk: The combined failure caused sudden loss of power while driving, engine stalling, and significant driveability hazards, creating an immediate risk of a rear-end collision on public roads. Confirmation & Inspection: The failure was confirmed and diagnosed by a certified service facility. Replaced components and diagnostic documentation remain available for inspection upon request.”

“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.”

“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.”