2021 Kia K5 Problems

What owners report

Owners of the 2021 K5 report two fairly distinct clusters: fuel-system complaints that most often appear at higher mileage and center on a swollen fuel tank, fuel odors, and refueling problems tied to a check valve, and an electrical cluster at very low mileage covering an intermittent blower motor and melting fuse-box connections, infotainment screen issues, and door-panel electrics. Engine, transmission and driver-assist complaints also appear, with transmission reports including harsh or delayed shifting and occasional loss of drive power.

1. 1
   Fuel system

   Fuel tank expanding or leaking, fuel odor, refueling trouble

   • 42 complaints (25%)
   • median 111,000 mi at 5.3 yrs old (13 state mileage)
   • 1 mention a crash, fire or injury
   • filed 2021–2026

   Complaints describe the fuel tank swelling or bulging, a strong gasoline smell, fuel spitting back out of the filler neck during refueling, and the fuel gauge dropping to empty or reading incorrectly. Several owners report a loud bang from the rear of the vehicle and gas leaking under the car; some say the dealer confirmed the tank had expanded and in a few cases declined to replace it. A number of owners link these symptoms to a recall notice for the fuel tank check valve. Reported mostly between about 50,000 and 200,000 miles, often during or shortly after refueling and sometimes while driving at highway speed.

   Recall 25V794000Recall 21V5190005 related service bulletins

   What to check: Ask whether the check valve and fuel tank service campaign or recall work has been completed, and look and smell for fuel residue around the tank and filler neck. After a fill-up, confirm the gauge and distance-to-empty read correctly and that fuel does not back up at the nozzle.

   2 excerpts from owner complaints in NHTSA records

   “My current 2021 Kia K5 FUEL TANK EXPLODED while driving. I’ve had this car for about 5 years and since driving it off the lot have experience issues with the vehicle and just a few hours ago, the fuel gas tank explode raising the back seat with passengers in the vehicle. It was extremely scary and something out of the blew. …”

   NHTSA complaint #11650792, filed 2025-03

   “I am reporting a violation of the National Traffic and Motor Vehicle Safety Act by Ball Kia (National City, CA). The dealer tried to deny service for recall 25V794000 (SC356) for a melted, leaking fuel tank, fabricated a false diagnostic narrative of road impact to exploit me, and tried to charge $3,000 out-of-pocket for a federally mandated free repair.My vehicle has a severe fuel leak from a compromised fuel tank. …”

   NHTSA complaint #11757545, filed 2026-08
2. 2
   Engine

   Engine misfire, shudder, stalling and oil loss

   • 44 complaints (26%)
   • median 52,000 mi at 4.6 yrs old (13 state mileage)
   • 1 mention a crash, fire or injury
   • filed 2020–2026

   Owners report the engine shuddering or sputtering under acceleration, intermittent check-engine lights with misfire or exhaust-related codes, and stalling at speed or at idle. Some describe oil leaking or being found across the engine compartment, and one case involved a drain plug coming loose leading to engine replacement. Complaints also mention coolant smells and leaks that dealers could not trace. Reported from a few hundred miles up to roughly 90,000 miles, with misfire and oil-loss reports common in the 40,000 to 90,000 mile range.

   3 related service bulletins

   What to check: Check oil and coolant levels and look for leaks or a sweet coolant smell after a test drive, and ask whether the thermal management module and engine software updates have been applied.

   2 excerpts from owner complaints in NHTSA records

   “Hi I brought my 2021 kia k5 got line last February 2023 around 44k miles I have had coolant leak where nobody can tell me where is the leak coming from I look online and other Kia owner have had the same issues”

   NHTSA complaint #11630045, filed 2024-12

   “I am submitting this complaint regarding ongoing and unresolved safety issues with my Kia K5, which I believe are directly related to a known recall involving the ECM (engine control module) and/or fuel system. My vehicle continues to jerk and misfire during acceleration, and it has even stalled at idle on multiple occasions — creating a serious safety concern for myself and others on the road. I have already completed the recommended repairs, including new ignition coils and spark plugs, yet the problem persists. …”

   NHTSA complaint #11676487, filed 2025-07
3. 3
   Transmission and drivetrain

   Hard or delayed shifting and loss of drive power

   • 14 complaints (8%)
   • median 32,077 mi at 4.6 yrs old (5 state mileage, few)
   • filed 2020–2026

   Complaints describe jerking and sputtering while shifting between low gears, hard or missed shifts with a grinding sound, and in some cases a complete loss of motive power while driving, requiring a tow and transmission replacement. A few owners report the problem returning after a replacement, and some note the dealer could not identify a cause. Reported from very low mileage up to around 100,000 miles, appearing at both city and highway speeds.

   Recall 22V7600004 related service bulletins

   What to check: Test drive through all gears from a stop and at part throttle, listening for grinding or hesitation, and ask whether any transmission software updates or replacements have been done.

   2 excerpts from owner complaints in NHTSA records

   “Transmission requires total replacement within 5 days of purchase of new car. Vehicle was parked when transmission fluid leak was discovered. It was driven back to the dealer, which is nearby, but this experience has shaken our faith in the safety and build quality of this 2021 Kia K5 gt-line.”

   NHTSA complaint #11385251, filed 2020-12, 298 miles

   “1. Car has completely lost power during normal driving. Transmission failure. Loss of Motive power. It is available for inspection upon request 2. Car lost all motive power while on the highway, car had to coast to a stop. This was very dangerous. 3. Car was taken to the Kia dealership, diagnosed by their techs, and transmission replaced. This has occurred two times since the car was purchased new. First at 4,600 miles (6/13/2021) , second at 16,600 miles (9/7/2022). Both times dealership replaced the transmission 4. …”

   NHTSA complaint #11488885, filed 2022-10
4. 4
   Electrical system

   A/C blower stops working; melted fuse or wiring

   Mentioned in 5 of 60 sampled complaints

   Owners describe the air conditioning or blower quitting intermittently, sometimes working again after hours or days. Several report that replacing the blower motor and resistor did not fix it and that the fuse for the blower, or the wiring harness at the fuse box, was found melted or burned. Complaints also mention dealers saying the fault could not be reproduced when the system happened to be working at the time of the visit. Reported across a wide mileage range, frequently in warm-weather use and often months into ownership.

   4 related service bulletins

   What to check: Run the blower on every speed setting and feel for consistent airflow, and ask whether the blower motor fuse relocation campaign has been performed. If the A/C has been repaired before, ask to see whether the fuse box or harness was inspected.

   2 excerpts from owner complaints in NHTSA records

   “My a/c has been giving me issues for about a year and a half to two years now. I have a 2021 Kia k5. When I first told Kia about it they told me it’s from the rain, if that’s the case then every car on the road would have this issue. Then they later told me it was my motor blower when I went back. There was a thousand dollar difference between two quotes they gave me for the same issue also. The air used to come on for a few hours or a day then go completely off. …”

   NHTSA complaint #11661465, filed 2025-05

   “AC stopped blowing, vehicle had 62k miles. Took to an autoshop and they indicated that the AC blower and resistor needed to be replaced. I have both of these replaced, the AC work for a few minutes and then stopped again. I took it back to the same shop and the mechanic indicated that the fuse box was melted/burned (I have a picture as evidence). This is a tremendous fire hazard and we have been leaving our car parked outside of our home out of fear that it will catch fire. …”

   NHTSA complaint #11603609, filed 2024-07
5. 5
   Electrical system

   Steering assist and driver-assist warnings cutting out

   • 22 complaints (13%)
   • median 38,538 mi at 3.2 yrs old (8 state mileage, few)
   • 2 mention a crash, fire or injury
   • filed 2021–2026

   Complaints describe the steering wheel suddenly becoming stiff or hard to turn, often together with a cluster of warning lights for lane keeping, adaptive cruise, blind spot and collision warnings. Some owners report lane keeping or lane assist engaging on its own and pulling the wheel, with the features reactivating after being switched off. Others report the systems working only intermittently. Reported at low to moderate mileage, often within the first 35,000 miles, and sometimes while turning at low speed.

   Recall 21V447000

   What to check: During the test drive, check that lane keeping, adaptive cruise and collision warnings behave normally and can be switched off and stay off. Ask whether the steering system recall work has been completed on the vehicle.

   2 excerpts from owner complaints in NHTSA records

   “The steering wheel became stiff all the sudden and became hard to turn. As well as all the warning lights came on when that happened such as Adaptive Cruise Control Automatic Emergency Braking Blind Spot Warning Forward Collision Warning Lane Departure Warning Lane Keeping Assistance Parking Collision Warning Rear Cross Traffic Warning. I was driving in the middle of the road when this happened and this could’ve caused a huge accident due to the fact that I couldn’t steer my car properly. No, the problem has not been resolved yet. …”

   NHTSA complaint #11717979, filed 2026-02

   “Since October these features have been on and off working when they want to. I don't know what is happening with the safety features but it needs to be fixed or a update is needed for all the safety features.”

   NHTSA complaint #11449212, filed 2022-01

Buying note. A 2021 K5 is worth a careful pre-purchase inspection focused on the fuel tank and refueling behavior, the A/C blower and fuse box, and transmission feel, plus confirmation that open recalls and service campaigns have been completed. Service records showing the fuel-system and blower fuse campaigns were performed are the most useful thing to ask for.

Summary written with AI from a sample of 60 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Where a problem shows a complaint count, every complaint for this model year was matched with fixed keyword rules (written with AI and tested against the sample), and the mileage, age and repair figures are calculated from those complaints; owners' figures are as stated, not verified. Other counts refer to the sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.