2023 Hyundai Ioniq 5: What to check before buying

A sudden "check electrical system" warning, often after a loud pop, is the core complaint, and dealers trace it to a failed ICCU. The car drops into a power-limited turtle mode and often dies, sometimes at highway speed. The 12V battery stops charging, so jump starts and new batteries help only briefly. Failures show up around 22,000 to 25,000 miles and recur after recall work. Repairs often take a week or more, and replacement ICCUs are back ordered. One fire report describes a charging pin melting during DC fast charging, and one crash followed brake failure in reverse.

Sudden loss of drive power is the main pattern, and most cases trace back to ICCU failure. A pop and a "check electrical system" warning come first, then speed is capped somewhere between 12 and 30 mph before the car stops. Some failures follow recall software updates or an earlier ICCU replacement. A second pattern appears after 50 to 60 miles of fast highway driving: the rear motor quits, power limited mode kicks in, and the car hesitates or lurches. Back-ordered parts stretch repairs. One crash involved the car lurching forward while stopping in a parking garage.

Unexpected surging and speed swings define this category. On the highway, often after about 50 miles, the car drops 3 to 5 mph with an unresponsive accelerator, then lurches back to speed, with or without cruise control. Two crashes involve sudden acceleration while pulling into parking spaces. Other reports describe the car creeping forward when Auto Hold disengages after a driver-assistance error, a false radar blockage warning that shuts off cruise and forward safety features, and brake lights that stay dark during regenerative braking.

Brake lights that stay off during regenerative braking are the main complaint. In i-Pedal and Level 3 regen, the car can slow hard with dark brake lights unless the accelerator is fully released, and owners report close calls with drivers behind them. Both crash reports appear to describe the same incident filed twice: after a shift from reverse to drive with i-Pedal engaged, the car rolled forward, the brake pedal went to the floor, and the car stopped against an electrical pole.

Driver-assistance faults and erratic behavior make up this group. Reports include sensor errors that disable cruise control, a misaligned camera the dealer would not cover under warranty, and condensation in front of the camera that makes the car jerk within its lane. Adaptive cruise has accelerated hard after setting itself to 85 mph. One report says automatic emergency braking failed to activate, though dealers found the system working as designed. Another notes that pressing the brake only pauses cruise control. One entry is an ICCU failure at highway speed.

Limp mode capped at 25 mph is the most common report here, caused by a failed ICCU, sometimes weeks after recall repairs or a new 12V battery. Owners describe a pop followed by a "check electric vehicle system" warning. Other cases include a 12V battery drained overnight by a faulty navigation head unit, a charging port that overheats and throttles charging even after a software update, and repairs stalled for weeks waiting on parts.

Severe vibration at highway speed is the pattern, traced to sound-dampening foam inside the original Michelin tires coming loose. The foam balls up, the tire will not balance, and the shaking can make the car hard to drive above roughly 45 to 60 mph. Onset shows up around 10,800 to 16,000 miles, and it can repeat on replacement tires. Shops and dealers often struggle to diagnose it. Owners end up buying new tires or having the foam removed.

Brake lights stay off while the car slows under regenerative braking. In i-Pedal mode and regen levels 2 and 3, the lights come on only when the accelerator is fully released or the brake pedal is pressed. The car can slow hard, even nearly to a stop, without warning drivers behind. Owners report near rear-end collisions and describe it as the default software behavior. Some have stopped using one-pedal driving because of it.