A deficient engine design plagues the mid-size sedan. The faulty 2.4L and 2.0L engines appear on most vehicles between 2011 and 2019. The Sonata also suffers from faulty safety sensors for its airbags and corroding connections in its electrical system.
Key Points
- While the 2018 Hyundai Sonata ranks fifth for mid-size cars by owners at Vehicle History, the sedan has a poor reputation for an engine known for seizing and fires.
- A class-action lawsuit awarded a lifetime warranty for the problematic Theta II engine. However, it doesn’t fix the underlying design flaws.
- Airbags and seatbelt recalls include bad passenger seat sensors, overheating wiring, and corroding control units. You may not be properly protected in an accident.
- A variety of steering and electrical flaws include sticking cruise control buttons and shorting computer boards that add to its questionable reputation.
- Newer model years avoid most of the problems associated with the catastrophic 2011 redesign, but still have that worrisome Theta II engine under the hood.
Most Concerning Problem on the Hyundai Sonata is the Theta II Engine, which is Subject to Knocking, Seizing, and Starting Fires
The biggest problem associated with the Hyundai Sonata from 2011 to 2019 is the 2.0L and 2.4L GDI engine. Since the debut of the Theta II engine design, there has been a constant string of investigations, service bulletins, and recalls.
Engine issues include knocks, seizing, bearings wearing out, connecting rods fracturing, and the potential for the engine to start on fire. The average failure occurs around the 90,000-mile mark.
In 2021, a settlement between owners of the affected sedans and Hyundai resulted in the implementation of a lifetime warranty on the blighted engine.
To qualify for the warranty, the vehicle must have a new knock sensor installed. The sensor will trigger the check engine light when it first detects signs of engine failure. This may prevent the need for an engine replacement, and get the driver to the shop before the motor overheats.
Just how bad is the engine? Out of an astounding 3,000 complaints filed with the National Highway Traffic Safety Administration on the 2011 Hyundai Sonata, nearly a third of them refer to engine problems. By 2015, overall complaints dropped to around 600, but engine issues represent more than half.
Faulty Seatbelts and Airbags are Another Major Concern for Nearly Every Model Year Since 2011
Other chronic issues that appear in nearly every year of the Hyundai Sonata since 2011 are its malfunctioning seatbelt and airbag systems. The front seatbelts in the 2015 model struggle to properly latch. The pre-tensioning system for front seatbelts from 2011 to 2013 was recalled due to the airbag system failing to sense a passenger in the seat.
A massive investigation opened in April 2019 regarding the airbag control units found in the 2013 to 2019 Hyundai Sonata. As the car ages, the control unit may corrode.
In some instances, the airbags failed to deploy during a crash as the wiring to the ACU was overloaded and did not send the signal to open the airbags.
This investigation includes millions of vehicles from multiple manufacturers. Any recall campaign resulting from it will be comparable in scale to the Takata airbag debacle.
Frozen Power Steering, Stuck Cruise Control, and Corroding Fuse Boxes Round Out the Most Common Complaints About the Hyundai Sonata
Unfortunately, the engine and airbags are not the only systems that present real problems to owners and drivers. The steering column gathered over 1,000 complaints in 2011 as it suddenly lost power while the car was in motion. A faulty control panel short-circuited.
A recall replaced the bad boards, but other owners continue to experience problems around the steering wheel.
Multiple drivers reported that their cruise control refused to engage unless they banged on the steering wheel. A faulty wiring harness inside the steering column prevents the circuit to close between the cruise control buttons and the computer.
Finally, an irritating and potentially dangerous issue is associated with the brake and headlights. Most of the comments are lodged after the sedan rolls past the 100,000-mile mark.
It is the most common complaint shared by drivers at Repair Pal. The fuse panel located under the dashboard starts to corrode. Various lights may not come on or stay on even after turning them off. Replacing the old fuse block fixes the issue at a price of around $500 to $800.
Cross the Earlier Years of the Hyundai Sonata off Your Short List, and Be Aware of the Theta II Engine’s Shortcomings
If the Hyundai Sonata is still on your list of possible used cars, avoid its worst years to minimize your future problems. By 2017, most of the chronic issues found on the 2011 to 2015 versions were addressed.
However, even a pristine 2018 will likely have the horrible Theta II engine. While it is warrantied for the car’s lifetime, you might spend an excessive amount of time at the repair shop.
Photos: Hyundai
