Problems · by component
2016 Hyundai Sonata engine problems
451 owner complaints to NHTSA about the 2016 Hyundai Sonata cite engine, 62% of all 728 complaints for this model year.
Complaints
451
62% of all complaints
Crashes
1
Reported by owners
Fires
19
Reported by owners
Injuries
0
Reported by owners
What owners say about the engine
Verbatim from NHTSA complaints, newest first
“I am filing a formal safety complaint regarding severe vehicle instability, structural safety risks, and dealership workmanship negligence following a federal safety recall engine replacement. My vehicle received a new engine block under a federal campaign at a local dealership. Immediately upon picking up the vehicle, the front suspension developed a severe, heavy mechanical knocking and bumping noise over road surfaces under 20 mph, making the vehicle structurally unstable and hazardous to drive. To perform this engine swap, technicians were physically required to drop the front subframe framework and disconnect the lower suspension linkages and steering column components. The dealership is actively trying to deflect safety accountability for an assembly error. They issued a new estimate attempting to charge me over $3,200 to replace the entire front strut and rear shock assembly, claiming it is a 'pre-existing wear-and-tear' issue due to mileage. However, I hold the dealership's official Multi-Point Vehicle Inspection report from when the car was first dropped off for the engine failure three weeks prior. In that mandatory baseline safety report, their own…”
“The contact owns a 2016 Hyundai Sonata. While the contact's daughter was driving 55 MPH, the engine seized. The contact stated that the failure had occurred while the contact's two minor grandchildren were inside the vehicle during the failure. The vehicle was towed to an independent mechanic. The vehicle was later towed to the dealer where it was diagnosed with engine failure. The contact was informed that the engine needed to be replaced. The manufacturer was contacted, and a case was filed. The contact was informed about the eligibility for the extended warranty under Campaign 953. The contact was informed that the repair was not covered under the extended warranty because the Campaign 953 was not completed. The failure mileage was approximately 60,436.”
“While driving on the freeway, the check engine light started flashing and the gas pedal became useless. This put the driver and the passenger of the car in massive danger as they could no longer accelerate on the freeway. Luckily, they were able to get off the freeway without causing an accident. Upon reading the code at an auto shop, they discovered that it was P1326 or a knock sensor issue. This malfunction caused the car to go into limp mode and put the passengers in serious danger. Several calls to the Hyundai Service Center were made yesterday (Saturday, October 3rd). However, not one was ever answered. They hope to be able to get the car to the dealership's service center as soon as possible, but the earliest appointment online is multiple weeks away. This same car was recently at the dealership service center for an internal engine oil consumption problem and thoroughly inspected. The car is up to date on all software and recalls. Even though a valve cover replacement fixed the oil consumption issue, the owners are now having even worse issues. This is the only car for a married couple who are both working and going to college full-time. This issue has…”
“I am concerned that the engine may seize or stall without warning while driving, creating a risk of crash, injury, or death. The Theta II engine defect is known to cause engine seizure, stalling, and fire. Hyundai has denied warranty coverage based on mileage and second-owner status — both of which are explicitly prohibited as denial grounds under the Settlement — leaving me driving an unsafe vehicle.”
“The vehicle experienced a Theta II engine failure at under 57,830 miles while driving on northbound [XXX] near the [XXX] Parkway U-turn in [XXX]. The engine made a loud noise and lost power. I was able to coast to the far right side of the U-turn under the bridge. I called HERO (Austin's emergency roadside assistance). They responded, determined it was not a battery issue, and pushed the vehicle to the Southern Leisure Spa parking lot on the southbound side of the road. The vehicle was then towed. The vehicle is equipped with the KSDS (Knock Sensor Detection System) software update, installed as part of Hyundai's remedy for this known defect. Despite KSDS being installed, the engine failed due to connecting rod bearing wear, consistent with the documented Theta II defect. A Hyundai dealership confirmed KSDS was installed but denied the warranty claim, citing maintenance records. The vehicle is available for inspection upon request. The Theta II engine defect has been the subject of prior NHTSA investigations and Hyundai recalls. This complaint is filed to document another failure of the same defect in a vehicle with the manufacturer's remedy installed.”
“Component & Inspection: Vehicle engine suffered connecting rod bearing failure and entered restricted P1326 "Limp Home Mode" (max 2,000 RPM). The vehicle is grounded and available for inspection at Bud Clary Hyundai in [XXX].Safety Risk: Sudden, unexpected loss of power occurred while driving, placing me and other drivers at immediate risk on public roads due to the vehicle's inability to maintain normal traffic speed or safely accelerate.Dealer & Corporate Confirmation: Active P1326 engine code is confirmed. Car has been held for 14 days. The franchise is violating federal settlement rules by explicitly refusing to execute the mandatory, free mechanical Bearing Clearance Test (BCT) unless I pay out-of-pocket fees.Inspection & Corporate Compliance Failure: Car was brought to the dealer on XXX. The service manager admitted in writing that they are withholding safety diagnostics to protect shop labor hours due to an automated computer flag regarding a clerical title brand discrepancy. Hyundai Corporate is actively enabling this violation; my case manager refuses to issue a manual compliance override for the safety test and is violating federal settlement terms by…”
Showing 6 of 451 reports. Read every report on NHTSA.gov.
Data from NHTSA Complaints API (owner reports, unverified) · synced Nov 10, 2026NHTSA vehicle page
Complaints are unverified owner reports to NHTSA and are not normalized for sales volume. One complaint can cite several components.