2021 Hyundai Sonata Problems

Going down the road driving the car lost power and went in limp mode with no warnings on the dash at all!

At approximately 130,000 miles, vehicle developed and internal coolant leak caused by a failed Exhaust Heat Recovery System (EHRS) in the center muffler assembly, matching TSB 23-EM-009H - a known manufacturing defect documented by Hyundai. Coolant has been slowly leaking internally into the exhaust system. The authorized Hyundai dealership initially failed to diagnose the internal leak and told me there was no leak and wanted to send me home. After pushing back, the internal leak was confirmed. If not caught, this defect could result in engine overheating or complete engine failure without warning. Hyundai Motor America has denied goodwill coverage despite this being a documented manufacturing defect.

DESCRIPTION OF SAFETY DEFECT & IMMEDIATE HAZARD:My 2021 Hyundai Sonata SEL is currently exhibiting the most severe, catastrophic symptoms of the fuel tank expansion defect covered under NHTSA Campaign 25V796000. The fuel tank has expanded so drastically that it physically warped the structural interior of the cabin, violently popping the rear passenger seat completely out of its assembly while the vehicle was in motion. Furthermore, there is a constant, heavy, raw gasoline odor inside and around the vehicle. The vehicle is a documented, active fire, explosion, and vapor inhalation hazard. It is currently physically located at Sterling Hyundai in Lafayette, LA.DESCRIPTION OF MANUFACTURER NON-COMPLIANCE & REFUSAL TO REMEDY:Hyundai Motor America and Sterling Hyundai are in direct violation of their legal obligation to provide a safe, accessible remedy or interim safety accommodations under federal recall guidelines. An Executive Case Manager from Hyundai Corporate has officially refused to provide a direct-billed rental vehicle or a dealer loaner.Initially, a third-party rental vehicle was provided. However, that vehicle was compromised in an accident and wrecked through absolutely no fault of my own. Despite my lack of fault, Hyundai Corporate and the dealership are now explicitly using that accident to refuse any further direct-billed rental accommodations or dealer loaners.Instead, they are demanding that I pay out-of-pocket for a rental vehicle at a rate of $60/day for a repair process expected to take multiple weeks, knowing I do not possess the upfront financial means to cover these costs. By imposing this insurmountable financial barrier due to an accident I did not cause, Hyundai has effectively stranded me. Because I must maintain my livelihood and have no other means of transportation, Hyundai’s bad-faith refusal to direct-bill an accommodation is actively forcing me to retrieve and operate a verified, explosive fire hazard.REMEDY SOUGHT:I request that the NH

The contact owns a 2021 Hyundai Sonata. The contact received notification of NHTSA Campaign: 25V796000 (Fuel System, Gasoline); however, parts were on back order. The contact stated that while driving at an undisclosed speed, the vehicle jerked with an abnormal gasoline odor inside the vehicle. An unknown warning light was temporarily illuminated. Upon further inspection, the contact became aware that the fuel level had dropped. The vehicle was taken to a local dealer where it was diagnosed with an expanded fuel tank. The contact stated that the O2 sensor, spark plugs, and ignition coils were replaced by a local independent mechanic; however, the failures persisted. The contact had headaches while driving the vehicle. Medical attention was not needed. The manufacturer was made aware of the failure. The failure mileage was approximately 100,000.

Transmission replaced twice and all of them continue to fail. Several Hyundai service centers are unable to determine the cause and are only able to update/relearn and replace whenever they are able to replicate the issue. The issue is that at a cold start, the car makes a popping sound, jerks and shakes. The car hesitates to accelerate. You can hear the noise of acceleration but RPM does not go past 3 and MPH doesn't go past 30mph. I'm unable to upload docs because of the upload limit. If there's another way to send docs, please let me know

Massive loss of coolant in closed loop cooling system Heat soak. Fail safe mode

The Left blinker switch keeps going in and out, working about 50% of the time. Both the light and the blinker sound do not turn on. When getting it checked out at an auto repair shop, the maintenance tech said this was more and more common for 2021 sonatas and it was not due to anything I did. It was a multifunction switch problem.

The car will idle high around 1200 rpms. The car will most of the times fix the issue when you turn the car off and back on but it will start again after driving. This is a known issue with the car. I have had the egr valve replaced since it will pop up the codes P240F and P049 for egr slow response and control position exceeded learning limit but the problem came back within two days. I did find a forum that deals with the joint connector repair but this needs to be a recall as I have come across many people who have this problem and paying out of pocket to fix it.

The internal core of the Exhaust Heat Recovery System (EHRS), part of the center muffler/front pipe assembly (#28600-L5210), suffered a catastrophic failure. This allowed approximately 9 gallons of engine coolant to leak directly into the hot exhaust stream. Safety Risk: This failure creates a severe visibility hazard. During acceleration from stop lights and stop signs, the vehicle emits massive, thick clouds of white glycol smoke. The smoke is so dense that it completely obscures the driver's view of trailing vehicles and prevents following drivers from seeing the roadway or my vehicle's brake lights, creating a high risk of rear-end collisions. Additionally, the rapid loss of coolant caused the engine to overheat and lose power while in motion, nearly causing a stall in active traffic. Confirmation: The failure was confirmed by the service department at Washington Hyundai (Invoice #174281). This is the second failure of this specific component (previously failed in Jan 2025). The manufacturer issued TSB 23-EM-009H for this defect, acknowledging it affects 2020-2023 Sonata Hybrids, but no safety recall has been issued. Symptoms: The issue was preceded by a "sweet" burning smell and a sudden "Engine Overheating" warning on the dashboard. The failed component has been replaced by the dealer, but the manufacturer refused to replace the coolant-poisoned Oxygen (O2) sensors, leaving the vehicle in a technically compromised state. The failed unit is likely held by the dealer for warranty parts return.

The EHRS coolant system failed and had a leak causing the coolant to be excessively burned off as thick white smoke. This caused me to not be able to see anything behind me and forced others to stop or slow down dramatically to avoid colliding with me. I had my engine overheat and force me to pull over on the side of an unsafe road because the exhaust system burned off my entire tank of coolant in less than a mile. I have taken this to a Hyundai dealership and they confirmed it was the EHRS system failure and told me it was a fairly known issue with the 2020-2023 Sonata Hybrids. I was told that even if I get it replaced the possibility of having it happen again are pretty high. This seems extremely unsafe to myself and others.

Massive loss of coolant in closed loop cooling system Heat soak. Fail safe mode

Will be driving the car and suddenly hear a beep. Then the dashboard will flash with the ABS light engine light tire pressure light check Blindspot sensors, forward collision sensors. once all the lights appear on the dashboard, I can no longer accelerate. i’ve cleaned the throttlebody. I’ve replaced the gas pedal and it’s still kicking back the same code it still does it the same identical thing. It’s given out on me three times since December with an infant in the car. We are now in February.

During a front end collision the car did not auto brake and the air bags did not deploy. The car has been totaled and is currently at a dealership for insurance appraisal.

Unknown

• I experienced trouble with my splash guard being damaged from hanging and scraping the ground about a month after purchasing the vehicle. Also, my hood paint started chipping after a recent cold front experienced in my state earlier this year. Yes it is available for inspection upon request. Regarding the splash guard, not applicable. • It’s was very inconvenient to drive with a portion of my car scraping the ground. I had to be more mindful of my driving in the higher speed limit areas incase the splash guard detached. I had it re-attached multiple times. Regarding the chipped paint, not applicable. • It it counts, for my splash guard, during a servicing, I asked Hyundai to re-attach it. For the chipped paint, no. • The splash guard has during a past servicing. The chipped paint is more recent so it hasn’t • No. Splash guard, a month after purchasing vehicle. The chipped paint, earlier this year, January-February 2026.

Sunroof exploded on the highway with no one in-front of me to kick up any rocks or debris.

The contact owns a 2021 Hyundai Sonata. The contact stated that while driving 10 MPH and attempting to make a right turn, the brakes independently activated. Neither the dealer nor an independent mechanic was contacted. The check engine warning light was illuminated. The contact stated that the failure had occurred on several occasions. The vehicle was taken to the dealer and an independent mechanic to be diagnosed. The manufacturer was not notified of the failure. The approximate failure mileage was 42,000.

Was driving in reverse out of garage and ABS brakes were applied like I hit a patch of ice stopping the car. Released when applied pressure to brake. Then while on highway going 60 miles an hour the emergency brake system went on for no reason applying pressure and red light came on the dash with a left facing arrow. System released within a few seconds but scared me and I still have to drive this car on highway.

P0471 error comes up off and on, this is recall related but the dealership refuses to address it. The seatbelt has to be clicked 2x in order to stick. Happens with driver side.

The contact owns a 2021 Hyundai Sonata. The contact stated that while driving at an undisclosed speed, his son complained that the seat belt had tightened and locked and that he was unable to adjust the seat belt. Upon arriving at his destination, the contact stated that attempts to remove the seat belt had failed and the contact decided to cut the seat belt. The vehicle was not taken to the dealer or an independent mechanic. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was 26,450.

After 9 months of ownership, on at least five (5) instances, the car has the following things happen at the same time: 1) all warning lights on the dashboard activate, 2) the battery discharge warning light activates, a loss of power steering, no speedometer, no cameras (rear or front), no AC, and all the safety functions are disabled including but not limited to: Forward Collision Warning, Parking Collision Warning, Automatic Emergency Braking, Lane Departure Warning, Rear Cross Traffic Warning. Yes, the car is available for inspection upon request. Safety is at risk by the loss of power steering and the deactivation of all safety functions. After each instance, the car has gone back to the manufacturer's dealer for inspection, they believed it might be an electrical issue after scanning for fault codes, but after 5 times, the dealer has not yet diagnosed the issue.

I leased a 2021 Sonata, and the Car has been a nightmare. My Car has been serviced by the dealership twice for a steering wheel that will not stop making noises. I am very concerned for my safety in this Car. The Wheel becomes hard to move. Also, last year, the Car was in the shop for four months while the forward collision sign needed to be fixed. The Car stopped twice. I am terrified to drive this car; it only has 9,200 miles.

The driver seat motor malfunctioned when pennies got jammed iin the unprotected/exposed seat tracks. Hyundai would not cover the warranty and charged me $2000.00 for repair. After complaining to the Hyundai National customer service they would not consider my point of contention that the unproteted/exposed tracks contributed to the failure. A professional mechanic stated that a fuse should have failed before the motor malfunctioned.

WE LEASE A 2021 SONATA SEL EQUIPPED WITH AIR BAG SYSTEM FEATURING AN OCS IN THE RIGHT FRONT SEAT. THE PURPOSE OF THE OCS IS TO DISABLE RIGHT PASSENGER SEAT FRONT AIR BAG WHEN IT DETECTS TA CHILD RESTRAINT SYSTEM OR SMALL CHILD IN THE RIGHT FRONT SEAT. RIGHT FRONT AIR BAG IS DISABLED TO PREVENT INJURIES TO A CHILD FROM A RIGHT FRONT AIR BAG INFLATION DURING A CRASH. MY WIFE IS ABOUT 4'10" TALL AND WEIGHS 135#. WHEN SEATED IN PASSENGER SEAT, SHE REQUIRES A CUSHION TO RAISE HER SO SHE CAN SEE OVER DASHBOARD AND OUT SIDE WINDOW. OUR SONATA IS EQUIPPED WITH MANUAL PASSENGER SEAT THAT IS RAISED TO HIGHEST POSITION. PROBLEM IS THAT WHEN SHE USES CUSHION, THE OCS LIGHT STAYS ON INDICATING THAT AIR BAGS ARE DEACTIVATED AND WOULD NOT DEPLOY IN AN ACCIDENT WHICH COULD CAUSE AN EXTREME SAFETY HAZARD TO MY WIFE. WE TOOK CAR TO DEALER SERVICE CENTER TWICE, AND WE CALLED HYUNDAI USA CUSTOMER SERVICE - BOTH SAID NOTHING COULD BE DONE. SMALL ADULTS LIKE MY WIFE SHOULD BE ABLE TO BYPASS THE OCS USING A SHUNT OR BYPASS SWITCH. WE FEED THIS IS A SERIOUS SAFETY HAZARD. EARLIER SONATA MODELS WERE RECALLED FOR THIS ISSUE.

Engine makes rattling and knocking noises. Transmission hesitates and jerks Suspension front struts and rear shocks are bad. Possible the isolators. Having horrible back pain when riding in car. Starter intermittently doesn't work Lane keep assistance goes over small bump in road will make car drive in opposite lane into on coming traffic. Took car to Tameron hyundai in Birmingham on the 29th of December 2025. Told them everything thats going on with the car. They did nothing about any of the issues. Car has 55,000 miles on it as that is when all problems have incurred. 60000 mile Warranty expires in February of this year.

The contact owns a 2021 Hyundai Sonata. The contact stated while driving 65 MPH and attempting to accelerate, the vehicle failed to respond with the check engine warning light illuminated. The contact also heard a knocking sound coming from the vehicle. The contact pulled over on the side of the road and turn off and restarted the vehicle and the vehicle started operating as designed. The vehicle was taken to the dealer and the contact was informed that the transmission and engine needed to be replaced. The manufacturer was contacted but offered no assistance. A case was filed. The failure mileage was 2,700.