When I started the car at 10pm , a loud pop was heard and warning lights on the dashboard indicated an electrical problem. I turned off the radio and anything extra that could use up power; during the next 45 minutes I took surface streets instead of the freeway to drive 22 miles back home and speed was limited to 40 mph. The next day the same warning lights were on the dashboard and speed was limited to 20mph; car lost power after 1 block. Car was towed to the dealer, where an ICCU failure and blown fuse in the engine was diagnosed by dealership and replaced.

While using Highway Driving Assist/Lane Following Assist on Interstate highways, lane markings frequently disappear on overpasses and in construction areas. When this occurs, lane-centering assistance silently disengages. The only indication is a small dashboard icon changing color. There is no audible warning, steering wheel vibration, or other prominent alert. The vehicle may begin drifting before the driver realizes steering assistance has been lost. Observed repeatedly on Massachusetts highways, including I-495 and I-290. This creates an unexpected and serious safety issue, potentially resulting in an accident. I had this happen during a recent trip, and multiple times the car wandered towards an adjacent lane. It caused me to lose confidence in the system, and to maintain constant vigilance, gripping the wheel tightly at all times. Had I not done so, I’m sure I would have had an incident. Who watches the dashboard all the time? The driver's eyes are supposed to be on the road ahead, especially when approaching an overpass. Had they incorporated an audible or tactile alert, this would have greatly increased the driver’s awareness and potentially avoid a crash. Since the system obviously knows when it has disengaged, it would be a simple matter to implement this. My preference would be steering wheel vibration.

ICCU failure. Car slowed ona busy street. Inspected by dealership service and confirmed ICCU failure. The pop sound and then check electrical system warnings.

While attempting to operate my 2025 Hyundai Ioniq 5, the vehicle abruptly displayed a 'Check Electric Vehicle System' warning accompanied by a critical red master service light on the dashboard. A diagnostic scan via the factory Bluelink app revealed a hard fault code: DTC P1A9096 (ICCU / DC-DC Converter malfunction). This failure occurred under 7,000 miles, following a previous total 12-volt battery system failure a month prior. Driving the vehicle with this specific code puts the driver at immediate risk of 'Turtle Mode' or a sudden, total loss of motive power while in motion. Living in a mountainous region where the primary thoroughfare (Highway 17) lacks shoulders, an unexpected power failure presents an extreme, unreasonable highway safety risk to myself and surrounding traffic. The vehicle had to be flatbed-towed to a dealership for an entirely new ICCU assembly

I pulled my car out of the garage and proceeded to drive up the street. I suddenly heard a weird sound and an emergency warning appeared on my dashboard stating to check vehicle electrical system. I immediately stopped the car and returned it to the garage. Upon turning the car on a second time to check the message a second message appeared saying “stop vehicle and check power supply”. I called Hyundai for a tow truck to have the vehicle towed to the dealer. When I turned on the car to back it out of the garage it got halfway out and the entire system shut down making everything inoperable including flashing emergency lights, windows etc. there was very little time between the warning light going on and the car becoming inoperable. The dealer diagnosed a failure of the ICCU system which has been reported for several years. A quick Google search reveals that many Ionic owners have experienced this failure. I was incredibly lucky that this occurred within a block of my house. The previous night I was driving home on the LA freeways. Had this failure occurred at night on the freeway it could have been life threatening as there is very little time to get to safety and the hazard lights and all electronics become useless. The dealer said that they will be replacing the ICCU system with a better one. If that is the case then why wasn’t this car recalled and the ICCU replaced?