2023 Hyundai Sonata: What to check before buying

A fuel injector sticks open or leaks. The engine then misfires, shakes violently, and loses power, often at highway speed. Many cars stall and will not restart, so they have to be towed. Cylinder #3 comes up repeatedly. Failures start as early as 1,330 miles, are common between 8,000 and 15,000 miles, and show up again around 30,000. Repeat failures on the same car are frequent, and dealers replace either one injector or the full set. Warranty usually covers the repair, though one owner paid north of $1,000. Backordered parts can keep a car off the road for days.

Most of these reports are about recall campaign 25V796000. Owners get the notice, but parts are not available, and some cars wait at the dealer for weeks. The underlying fault involves the gas valve or EVAP valve sticking. The fuel tank swells, a loud slam comes from under the rear floor, and the fuel gauge suddenly reads empty. Repairs include replacing the valve and updating the ECU, and one owner reports downshifting problems afterward. Another car stalled at highway speed from a failed cylinder #3 injector, and the failure came back after repair.

Two problems dominate. The first is sudden power loss or a full shutdown while driving, with misfire codes, a flashing check engine light, or a "Hybrid System Failure" warning. Dealers often trace it to a fuel injector, but sometimes find no code at all. The second is an internal coolant leak into the exhaust. It causes white smoke, a heater that stops working, rapid coolant loss, and overheating. Dealers point to a service bulletin and a redesigned part, and one owner was billed $1300. Some cars sit for weeks waiting on recall work.

At highway speed the car loses power and the RPM climbs, but the car does not speed up. The dashboard lights up, and restarting brings the engine back. Code P065312 recurs, and dealers often cannot reproduce the fault. The push-button shifter is the other concern. It drops from Drive to Park while moving, fails to engage Park, or leaves the car in the wrong gear on an incline. That led to 3 crashes into parking blocks, a garage door, and other objects. N Line dual-clutch cars hesitate on takeoff and go into limp mode.

The car loses all power, the dashboard lights flash, and the engine shuts off at intersections or when shifting to Park or Reverse. Restarting is the only way to recover. Dealers often find no code, though one repair cost $1,800. Other reports describe the media screen blacking out, and a 1.6T battery that went dead after 10 days parked, which the owner blames on a stock battery too small for the drain from onboard computers. One hybrid leaks water through a door and into the trunk. Long recall repair delays also come up.

While parking, the car surges forward without warning. That caused 2 crashes. In one, the car hit a wall, the driver broke an ankle standing on the brake, and the car was totaled. In the other, it went over a low wall into a neighbor's yard. Other reports describe hesitation and sudden loss of acceleration on the highway. The RPM rises, but the car barely reaches 40 mph. Dealers find no error code, and one responded with a 12V battery management software update.

The emergency brake engages on its own at highway speeds of 60 to 70 mph with no vehicle ahead, which sharply slows the car and creates a rear-end risk. One owner reports it happening 3 times. The radar sensor behind the grille logo gets covered by snow and ice and stops working in bad weather. Adaptive cruise control can also react harshly when a car cuts in, braking and then downshifting and accelerating hard. Dealers show little concern.

Both reports trace steering trouble to other failures, not to the steering gear itself. In one, the engine shook and lost all power at 9500 and again at 19,000 miles, which made the car hard to steer. The dealer replaced spark plugs and cleaned cylinders without finding a root cause. In the other, cold weather knocks out power steering and every driver-assist feature at once. When steering assist suddenly returns, the car can swerve into another lane. The dealer has reproduced this fault repeatedly.

Brakes wear out unusually fast on the N Line. One owner reports 4 brake jobs, rotor replacement and resurfacing, and failed calipers by 40k miles. Replacement calipers were on back order for 2 months from Korea. The other complaint in this category actually describes a forward collision warning followed by power loss and a list of codes, with the dealer suspecting the ECM. It also mentions a 2023 Hyundai Santa Fe, so it may not apply to this car.