2017 Hyundai Santa Fe vehicle speed control problems

“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.”

“Directly after the dealer, Johnson Hyundai of Apex, completed Service Campaign 9C2 on 4/28/26, my vehicle began sticking, surging, and harshly changing gears. I have followed up with the dealer multiple times. They said they are not getting back any diagnostic error codes (outside mechanic shop also confirmed they're also not seeing error codes), but went ahead and recalibrated the ECM. They told me to drive for 200 miles and the issue should be resolved. I have now driven 1,500 miles and the issue persists. I'm now seeing Hyundai put out a 'Driveability Communication" about this issue, but there is no proposed fix/recall. This issue did not exist before this service campaign was performed by the dealership.”

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

“Hyundai Campaign 9C2 recall update: Took my vehicle in to have the Hyundai Campaign 9C2 recall update performed on the vehicle on June 9th, 2026. Since the update the vehicle is hesitant/jerky upon first drive of the day or anytime it sits more than a few hours. Occasionally it will do this while I am driving. I feel it is a saftey risk because this could cause my vehicle to abruptly hesitate without braking and cause someone to hit me, or worsetransmission to fail while at highway speeds. I took it back to the dealer that performed the required update around june 23rd 2026 and informed them of the problem caused by the 9C2 campaign update.I got the we don't know anything about it causing problems runaround. Even though it has been documented that dealers were notified of this problem. They then wanted to charge me a $100 diagnostic fee to see if it might be something else, I declined that because I know it is from this update. My vehicle ran perfectly fine and smooth before this update was applied and no CEL lights are on. I did this update because it was required to be done by Hyundai. When I started researching why my vehicle was hesitant/jerky after the…”

“The contact owns a 2017 Hyundai Santa Fe. The contact stated that while driving approximately 15 MPH on the interstate, the contact heard an abnormal tumbling sound coming from underneath the vehicle. The contact noticed an unknown object had detached from the vehicle. Upon inspection, the contact determined that the detached component was the radar sensor. The Automatic Emergency Braking (AEB) system and the adaptive cruise control became inoperative. The contact stated that the vehicle had not been involved in a crash prior to the failure. The vehicle was taken to an independent mechanic for inspection. The mechanic advised that the radar sensor could not be reattached and stated the failure was possibly caused by a crash. The local dealer was contacted, but the vehicle was neither diagnosed nor repaired. The manufacturer was not informed of the failure. The failure mileage was approximately 130,000.”

“After the installation of the Service Campaign 9C2 engine update, the car now seems to surge or rev up briefly at lower speeds like it can't find the right gear or is trying to briefly accelerate. It doesn't seem to be as noticeable at highway speeds, but in residential or low speeds, it's very noticeable and a little unsettling as the car feels like it wants to briefly lunge forward. No lights are on the dash and there is no indication of any malfunction, but it did not behave this way prior to the 9C2 engine program update. I waited for a couple weeks before contacting Hyundai Corporate about this issue because I was hoping maybe the transmission or engine was relearning after a battery disconnection, but it has not gone away.”