2016 Hyundai Sonata power train problems

“Went from 65 and dropped down to 40 going up grades on the freeway. Started shaking, check engine light went on and electric battery disappeared from dash. Got to top of grade, went back to normal. Problem repeated on next grades. Car had just left dealership lot an hour prior where it was safety inspected and they said all was fine. Took back to dealership for inspection and they said that there were no codes showing for what happened and all was well with the vehicle, when obviously it was not.”

“The following mandatory software update was performed on my vehicle: ECU SOFTWARE UPDATE FOR THETA II EMISSIONS IMPROVEMENT (SERVICE CAMPAIGN 9C2). After this update my vehicle drivetrain is quite erratic. In particular when the engine is cold it appears to jerk even when in Parking gear position. When cold the drivetrain experiences erratic gear shifts. This provides little confidence when driving and could result in safety issues when merging into traffic. Once the engine has reached its normal operating temperature it still makes occasional gear shift that are jerky and probably not good for the transmission. This vehicle had a very smooth transmission prior to the ECU software update, now I am hesitant when I need to merge into traffic, since I am not sure it will select the correct gear when accelerating. I have reported this to the dealership and Hyundai corporate service center and both indicate that when the engine is cold that the drivetrain can act strange, but once it is up to temperature it should be smooth. I have looked on the web and noticed multiple Hyundai owners with similar engines reporting the same issue after this software update. Hyundai…”

“My 2016 Hyundai Sonata is experiencing severe oil consumption due to a known Hyundai engine defect. The engine burns oil rapidly and loses more than a quart between oil changes. This creates a safety hazard because the engine can stall, seize, or fail while driving. The Hyundai dealership did NOT perform the official Hyundai oil-consumption test. They only checked the dipstick, noted the oil was low, and submitted a request for a paid combustion cleaning. Hyundai declined to pay for the cleaning, and the dealership is refusing to perform the required oil-consumption test unless I pay $750.00. Hyundai Corporate also refused to authorize the test, stating the vehicle is out of warranty, even though this is a known engine defect affecting many Hyundai vehicles. Without the official test, Hyundai will not review the engine defect or consider a goodwill engine replacement. This is a safety issue because the engine can fail without warning. The dealership and Hyundai are refusing to perform the required diagnostic test unless I pay $750, and refusing to review the defect without that test.”

“I have a car covered by the Theta II Settlement. Engine, fuel system. Metal shavings found in oil and oil is diluted with fuel and oil if overfilled 1 inch above full mark on dipstick upon pickup from dealership. The vehicle is available for inspection at my residence; however, it is currently grounded as a known safety hazard. The vehicle is exhibiting symptoms of imminent engine failure (audible knocking, P0011 code, and oil dilution). Despite being shown evidence of this(photo and video of oil overfill and watery viscosity) , the manufacturer instructed me to continue operating the vehicle, placing myself, and other drivers at risk of a high-speed collision or vehicle fire. The symptoms (P0011 code and engine noise) were confirmed by an independent mechanic on March 25th 2026. However, during the official Bearing Clearance Test (BCT), the dealership intentionally overfilled the engine oil by 3 quarts (documented via photograph) to muffle mechanical noise and artificially pass the diagnostic and issued a pass on all inspections despite the oil hazard. Hyundai Corporate Case Manager Nikulmar Dhabi has admitted on record that the dealer was out of compliance by…”

“This complaint is NOT related to the existing recall associated with this vehicle. The vehicle is experiencing a serious loss of power and acceleration issue. The car is unable to accelerate past approximately 60 mph. When pressing the accelerator fully, the vehicle does not respond or increase speed. While attempting to accelerate, the engine RPM increases and then suddenly drops repeatedly, causing the vehicle to struggle to maintain speed. This behavior is consistent and occurs during normal driving conditions. This creates a dangerous situation, especially when merging onto highways or attempting to accelerate in traffic, as the vehicle cannot respond when needed. The issue has occurred multiple times and makes the vehicle unsafe and unreliable to operate.”

“The contact owns a 2016 Hyundai Sonata. The contact stated that while driving and depressing the accelerator pedal, the vehicle failed to respond or exceed 30 MPH. The contact stated that the speedometer reading was lagging. The contact stated that the vehicle accelerated as intended while depressing the accelerator pedal with more force. The vehicle was taken to an independent mechanic, where the camshaft position sensor was replaced. Additionally, the contact stated that the starter was previously replaced due to the engine's failure to turn over while starting the vehicle. The contact stated that upon switching to Sport Mode and driving 40 MPH, the vehicle jerked and lost motive power. The contact shifted to neutral(N) and was able to pull to the side of the road. The vehicle was able to restart the vehicle, but the vehicle was undrivable. The vehicle was towed to an independent mechanic, where it was determined that the failure could be an electrical failure or that an engine replacement was needed. The vehicle was not repaired. An unknown dealer was notified of the failure, but the vehicle was not diagnosed or repaired due to the cost. The manufacturer was…”