Which parts fail
Components named in complaints (engine, cooling system, oil leaks, timing chain, exhaust).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2021 Kia K5 owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2021 Kia K5. The contact stated that while driving approximately 45 MPH, the vehicle jolted forward three times and then lost power. The contact stated that while driving at approximately 60 MPH, the check engine warning light illuminated. The contact steered the vehicle into an independent mechanic and the vehicle was inspected, and there was oil all over the engine compartment. The vehicle was taken to a dealer, where it was diagnosed, and determined that an unknown sensor was inoperable and needed to be replaced. The vehicle was repaired, but the failure recurred the same day the vehicle was retrieved. The vehicle was taken to the same dealer where it was diagnosed, and determined that the valve cover needed to be replaced. The vehicle was repaired, but the failure reoccurred nine times, and the valve cover was replaced each time. …
The contact owns a 2021 Kia K5. The contact stated that there were failures with the spark plugs. While driving at an undisclosed speed, the vehicle shuddered, and the engine sputtered. The contact stated that fuel spewed out of the filler neck while refueling the vehicle, and the fuel gauge incorrectly indicated that the fuel tank was empty after refueling. Additionally, there was an abnormal egg and sulfur odor coming from the vehicle with the check engine warning light intermittently illuminated. The contact stated that the vehicle was taken to a local dealer and inspected under NHTSA Campaign Number: 25V794000 (Fuel System, Gasoline). During the inspection, the seats were damaged. The vehicle was not repaired. The manufacturer was notified of the failure and was negotiating a buyback. The failure mileage was approximately 120,000.
The contact owns a 2021 Kia K5. The contact stated that the check engine warning light remained illuminated with DTC: P0471 displayed. The vehicle was included in NHTSA Campaign Number: 25V794000 (Fuel System, Gasoline) and was taken to the dealer for the recall repair where the dealer replaced the check valve. After receiving the recall repair, the check engine warning light remained illuminated with DTC: P0471 displayed. The vehicle was returned to the dealer, who diagnosed that the Exhaust Pressure Sensor was causing the Exhaust Gas Recirculation (EGR) Sensor to fail and needed to be replaced. The vehicle had not been repaired. The manufacturer was made aware of the failure. The failure mileage was approximately 52,000.
The contact owns a 2021 Kia K5. The contact stated that the driver-side turn signal became inoperable. The vehicle was shifting hard and/or not shifting at all. While driving at unknown speeds, the vehicle shut down. The turn signal and brake lights were illuminated. The contact stated there was a recall for NHTSA Campaign Number: 25V794000 (Fuel System, Gasoline). The vehicle was taken to the local dealer for diagnosis of the signal light. The vehicle was repaired, but the failure recurred. The BBB was contacted who filed a claim. The manufacturer was contacted, but no assistance was provided. The failure mileage was approximately 56,000.
The contact owns a 2021 Kia K5. The contact stated that while driving approximately 55 MPH, the fuel gauge suddenly went from one-half tank to empty. The fuel level displayed 120 miles to empty. The contact attempted to refuel the vehicle but was unable to add fuel to the tank. The contact also stated that the oil warning light and the TPMS warning light was illuminated. The contact associated the failure with NHTSA Campaign Number: 25V794000 (Fuel System, Gasoline). The local dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 119,185.
The contact owns a 2021 Kia K5. The contact stated while driving at an undisclosed speed, the vehicle shuddered. The check engine warning light was intermittently illuminated. The failure occurred on several different occasions. The vehicle was taken back to the residence. The vehicle was taken to a dealer to get a diagnosis however, the failure cause was unidentifiable. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 86,000.
The contact owns a 2021 Kia K5. The contact stated that there was an abnormal odor of fuel. The check engine light was illuminated. The contact received the recall notice for NHTSA Campaign Number: 25V794000 (Fuel System, Gasoline). An unknown local dealer was contacted, but the vehicle was not diagnosed or repaired. The manufacturer was contacted, but no assistance was provided. The failure mileage was approximately 200,000.
The contact owned a 2021 Kia K5. The contact stated that while driving at an undisclosed speed, the vehicle stalled. The failure was a recurring failure. The message "Not Emissions Ready" was displayed. The vehicle was towed. The dealer was contacted; however, the vehicle was not diagnosed or repaired. The manufacturer was made aware of the failure. The failure mileage was approximately 20,000.
While driving on my way home from work my , brakes became extremely hard to press down on and then my service engine light came on this all occurred on 7/31/2024. So the very next day I took my vehicle to a Kia dealership which was 8/1/ 2024 to find out what was causing this to happen. The technician stated that they would have to put it on a machine and run a diagnostic on it. I asked the technician while they were doing that to change the oil. I also realized that the oil light for my vehicle has NEVER came on since I purchased the car. So the technician did the diagnostic and stated that my vacuum pump had went out but he couldn't tell me why or how this had happened. I then took the vehicle to my parents house and left it there in the garage for a few weeks to have second opinion done. …
On [redacted] I took my automobile, a 2021 Kia K5 to Planet KIA of Charlotte NC located at 4700 E independence Blvd. I took it there to check what caused my engine light to activate. The initial diagnosis was a bad Sensor-Differential Pressure. Planet KIA repaired the Sensor-Differential Pressure at the cost of $501.17. My extended warranty company Route 66 covered $350.28 while I covered the remaining balance of $150.89. The engine light came on again the next day and while driving back to the dealership, I experienced the car slowing down and difficult to gain speed in highway traffic. I returned the automobile to Planet Kia of Charlotte and on [[redacted]}, I was informed that I had a valve failure which in turn caused my gas tank to swell. On [redacted] the warranty company denied request to pay for repairs due to their policy of not covering emissions which pertained to the valve. …
Engine complaints in other K5 years
Frequently asked questions
How common are engine problems on the 2021 Kia K5?
NHTSA has 32 complaints about the engine & cooling of the 2021 Kia K5, 19% of the model year's 169 complaints. The component named most often is exhaust system › emission control › gas recirculation valve (egr valve) (1 mentions).
Is there a recall for 2021 Kia K5 engine problems?
No. NHTSA lists no engine & cooling recall for the 2021 Kia K5, though it has 6 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2021 Kia K5 engine problems start?
Half of the complaints with a recorded mileage happened before about 52,000 miles, and 36% before 25,000 miles.
Is it dangerous?
Owners linked 0 crashes, 1 fire and 0 injuries to engine & cooling problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.