2025 Hyundai Ioniq 5 power train problems

“I am writing to document my case regarding my leased 2025 Hyundai Ioniq 5 XRT. Vehicle: 2025 Ioniq 5 XRT, VIN [XXX] Lease start / delivery date: Odometer: 4,368 miles Servicing dealer: Stevinson Hyundai, [XXX] Case number: XXX What happened: On Saturday, XXX, while I was driving, the vehicle displayed "Stop vehicle and check power supply" with the red 12V battery warning and the master warning light, and power was limited to approximately 25 mph. The high-voltage battery was at 66 percent. I was able to get the vehicle home at reduced speed, and Hyundai Roadside Assistance towed it to the dealer the same day. The symptoms are consistent with an ICCU failure, pending the dealer's diagnosis. Photos of the instrument cluster are attached. I consider a sudden loss of drive power at 4,368 miles to be a safety-related defect, and I have reported it to NHTSA. My situation: This is one of two vehicles in our household, and both of us need to get to work. The dealer is about 30 miles from my home. I am without transportation as of September 19. What I am requesting: 1. Written authorization for a rental vehicle starting immediately and continuing until my vehicle is…”

“I started the car and got the warning "check electric vehicle system." The car then lost power. It would only go 27mph with the accelerator pedal pushed all the way to the floor. My safety was at risk because my car was not responding appropriately to driver input. The car is at the dealership as it is undriveable in this condition. This is the second incident with this vehicle within 6 months.”

“I was slowing down, actively pressing the brake pedal to bring the vehicle to a full stop. As the car decelerated to what my senses and perception registered as a full stop, I pressed the “P” (Park) button while keeping my foot on the brake pedal. I felt the physical click of the “P” button under my thumb while still holding the brake, and my mind registered that the vehicle had successfully transitioned into Park. Before turning around, I visually confirmed that the vehicle had come to a complete stop. Believing it was fully secured in Park, I turned my head to check on my child in the back seat and naturally released the brake pedal completely. However, the system had actually rejected my command. I assume that the vehicle likely still had a small amount of speed at the exact millisecond I pressed the button, and the computer automatically blocked the “Park” command and kept the car in gear. Because an electric vehicle operates in almost complete silence, with no engine noise or vibration to indicate that it is still in gear, there was no auditory or physical cue to alert me that the car was moving when I released the brake. While my attention was turned…”

“During a family road trip, my 2025 Hyundai Ioniq 5 (~9,000 miles, less than one year old) suddenly showed red "Check Electric Vehicle System" and 12V battery warning lights and then completely lost power. The 12V system failed entirely - the vehicle could not be driven or shifted, and the doors and the rear hatch could not be locked or unlocked. It had to be flat-bedded to a Hyundai dealer because it was completely inoperable. The dealer diagnosed a failed ICCU (Integrated Charging Control Unit) and a blown ICCU safety fuse (fault code P1A9096) and is replacing both under warranty; the component is available for inspection. The ICCU converts high-voltage battery power to charge the 12V system; when it fails, the vehicle loses all electrical power and drive capability. The warning lamps appeared immediately before total power loss, with no prior symptoms at the last scheduled service. This is a known, safety-critical failure on this platform: a sudden, complete loss of power can strand occupants and, if it occurs while driving, cause loss of motive power - a serious crash risk. My vehicle was stationary when it failed, but the same failure at speed would be…”

“Vehicle was parked in closed garage overnight. In the morning I tried to start the car and it was unresponsive. key fobs, digital keys, NFC cards none of them were able to open the car. Used a physical key to open the door, and then tried to turn the car on, nothing worked all screens remained black and car was unresponsive. AAA confirmed that the 12V battery was fully dead. When they jumped the vehicle we heard a pop in the car, which is a known ICCU failure indication. The car still turned on and was drivable. I got it to the dealership safely and they confirmed that the 12V battery was fully dead and car only turns in if jumped. They also confirmed that the ICCU had a failure as well and they are going to need to replace the entire battery pack/ICCU assembly.”

“Car charged as scheduled overnight 3/28/26 but was dead the morning of 3/29/26 and when it was jumped gave error "Battery overheated, please stop and exit vehicle" and "check electrical system" - vehicle has been in shop for 16 days, no diagnosis except that it "probably" needs a HV battery.”