2020 Hyundai Sonata

In early May 2025 while driving around 40mph, I heard a very loud pop which startled me. Pulled over and looked back and noticed my backseats were push up out of place. I attempted to put the seat back into place but it wouldn’t fit into the latch anymore. The framing underneath the seats looked pretty damaged so I took it to a local mechanic. After doing some research, he found information for a check valve/fuel tank recall (Service Campaign 9B1) and then advised me to go a Hyundai dealership. I attempted to take it to the dealership, whom sent me away after I advised them of what happened. I came back the next day asking them to take a look at while informing them about the recall that could be related. Later that evening, they called and said the issue was directly related to the recall and the repairs would be covered. My car was in their possession for from 5.12.25 to 7.25.25 without any updates or instructions on what is happening. I was told they’re waiting to hear back from Hyundai Manufacturer on how to proceed. They returned my car to me on 7.25.25 stating everything was repaired. On 7.31.25 they called me back stating my tank needs to be replaced and bring the car back asap. My car was again being repaired and was returned to me on 8.25.25. Now my vehicle will not start randomly sometimes. At this point, I’m under the impression my vehicle is no longer safe as all the issues I’ve been facing are fuel related.

Whille driving back to Washington state my car check engine light came on and the car shut off while I was driving. I had to have it towed to the nearest city whi ch was Laramie Wyoming. There is no Hyundai dealer had to drive the car once it started back up to Cheyenne Wyoming it was checked. My on star told me there was a problem DTC P0145100 the status had red triangle the DTC power system powertrain and the DTC sub system EMS. I was told and given paperwork by the dealer and was told the car would need major repairs and could take up to 21 days once the work started it would have to he completed there because Hyundai had campaign dealing with my cars problem. I was told I could drive the car home but if the check engine light is flashing pull over immediately. My car is now at the 3rd dealer when I took it to Korum in Puyallup they did not have anyone to diagnose the vehicle only update onboard computer. They said and documented nothing was wrong with the vehicle which is inaccurate. I told Korum about the paperwork from the dealer in Cheyenne they did not so much as look at it. I took the car to the Dealership in Auburn Washington they to had the same findings as Wyoming also there was additional findings which corresponded with the smell of gas and my tank going empty after filling and trying to fill tank because was showing low fuel warning. Pictures were taken of the gas tank which had expanded as well as other pictures of the findings. I was told in Wyoming and Auburn that the code and findings are consistent with the Hyundai campaign

Something went wrong in the fuel tank that caused it to become so pressurized that the tank expanded up and out so far that it pushed the exhaust pipe down and my back seat of out place. The only issue I had was the car was accelerating slower than usual but it wasn’t even enough of a difference for someone who didn’t drive it every day to be able to tell. It did this for two days then the check engine light came on and it just read “powertrain”. Began slow acceleration on 06.08.2025. Check engine light came on the night of 06.09.2025. I took it to the dealership 06.10.2025. I immediately took it into the dealership and they told me the car could have exploded. There was a previous recall for the fuel pump that I had replaced at the dealership. After seeing my car, they said their techs and the techs at HMA have never seen one this bad and that maybe after replacing the recall part the system update failed in my vehicle and the issue was never actually resolved.

I received a notice in the mail my car needed a software update. I went to the dealership to have the update performed. They informed me there was a service campaign for an expanding fuel tank due to pressure. They were unable to return my car to me at that time stating they were awaiting direction from Hyundai Motor of America for the fix. The fuel tank expanded so much it bent the body of of the car underneath the backseat. It also broke the support straps. The dealership stated it was a known issue with a vent valve. Causing the fuel tank to swell so much it damaged the body. They have had my vehicle for 9 weeks with no direction as to what to next.

It was about 100 degrees outside yesterday, and while trying to pass a car, I look in my rearview mirror and notice there is fuel shooting out from my fill hose under my gas flap. I lost over 3 gallons of fuel on the road. This happened my whole 60 mile trip. This has happened to me before, but the temperature was around 76 degrees and it does not happen in cold weather. I have a feeling my fuel tank is expanding because when I took out my back seat where my fuel tank is located, the body of the car is all buckled up to the point where I can't get my backseat to latch down anymore. My car is available anytime for inspection upon request. I have not taken it to a dealer to get it looked at, there has not been a police report filed. And there were no warning lights or indicators other than a popping sound coming from my backseat area before the problem occurred. There are no warning lights or indicators after the problem either. I feel like I'm driving a bomb because my fuel tank could blow up at any time. This problem can be reproduced anytime by filling the tank and driving it in 90 degree weather.

I experienced an issue where the gas tank in my 2020 Sonata began to swell and emit loud popping noises while the vehicle was parked. I took it to the dealership, and Hyundai corporate eventually acknowledged the issue and agreed to buy out my loan. However, no official recall has been issued for this model year. This problem has had a major impact on my life. I lost my job due to not having transportation for over two months, and the stress of not knowing whether my vehicle was safe made it even worse. I had to upgrade my insurance for a loaner I never received, take financial hits, and go into deeper credit trouble—all while also recovering from a serious injury from a previous car accident. I now have to start over with a new loan while my credit is already damaged. I’m submitting this report not just for myself, but to ensure that other 2020 Sonata owners are protected and made aware of this issue. I believe this is a serious defect that warrants official investigation.

My wife and son experienced a terrible situation on the way home from training. They had to stop at the nearest gas station due to the vehicle showing extremely low gas in the tank during a short drive home. The fuel gauge initially showed about half a tank but drastically dropped on the way home. They stopped at a gas station to add fuel but during the process, fuel starting spewing out of the tank. The vehicle was scheduled to be dropped off at a later date for an open recall (service campaign 9B1). I called the dealership and told them I needed to get the vehicle in right away due to the incident. After bringing the vehicle to hyundai, they told me that the fuel tank exploded causing the tank to swell all the way around. Because the tank is located under the rear seat, we constantly heard air coming in due to the rear seat not seating properly. The check engine also was on and we smelled fuel while driving the vehicle. Hyundai representatives has been avoiding my calls to the point where I had to go in person for an update. Apparently, a district manager had to come inspect the vehicle to advise the dealership how to write up the request to send to corporate.

On or about November 13, 2024 our Hyundai Sonata 2020 gas tank almost exploded. We drove our vehicle to a dealership so that it could be checked because we kept hearing something that sounded like a loud pop / thumb underneath our vehicle. We had already been receiving notifications of a powertrain issue with the vehicle for years (without the dealership resolving the issue). So we were taking the vehicle in for numerous reasons when, the minute we drove our vehicle into the service bay (of a new and unrelated dealership) we were told that Hyundai's Corporate branch has ordered our vehicle grounded and told us we COULD NOT LEAVE with our vehicle or drive our vehicle off the dealership's lot. We were advised that our vehicle had almost exploded and that we were lucky to have brought the vehicle in. We were told that our vehicle should have never left the lot the day we purchased it brand new. We were told that our vehicle's backseats had detached and separated away from the frame of the vehicle. Our vehicle has been at the dealership since the day of the incident (e.g., on or about November 13, 2024). Our vehicle is still under factory warranty and powertrain warranty and Hyundai was not given us an end in sight or advised the public of the issue with their vehicles. WE were told that the vehicles needs repairs such as: 1. The vehicle needs the fuel tank assy and all of the parts for the tank, check valve, and campaign sticker: Please see TSB: 24-01-02OH