I own a 2021 Hyundai Sonata 1.6T, which has an open NHTSA safety recall (25V796000) related to fuel tank pressurization and fire risk. I brought the vehicle to an authorized Hyundai dealership due to a check engine light, reduced performance, and DTC P14EE, which aligns with the recall condition. The dealership refused to treat the concern as recall-related unless I paid a diagnostic fee and…
2021 Hyundai Sonata powertrain problems
moderate 21 complaints filed with NHTSA · avg repair $2,500 · see powertrain across all vehicles →
Complaints
21
Recalls
0
Avg fix
$2,500
When does it fail?
Of the 21 powertrain complaints filed for the 2021 Hyundai Sonata, here's the actual mileage breakdown — failures cluster heaviest at 0-25,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
The failure pattern owners describe
Buyer takeaway: The 2021 Hyundai Sonata has a documented pattern of transmission control issues that persist even after manufacturer recalls and component replacement, with owners reporting continued power loss, shifting problems, and shifter malfunctions at relatively low mileage. Fuel system pressurization and coolant loss issues add to the safety concerns documented in NHTSA complaints.
Owners of the 2021 Hyundai Sonata consistently report transmission control failures that recur despite recall repairs and part replacement. Multiple owners describe sudden loss of power while driving, with the vehicle entering fail-safe mode or refusing to accelerate when the pedal is pressed—events occurring between 2,700 and 41,000 miles. One owner's transmission was replaced under warranty at just 2,212 miles, then the same vehicle exhibited shifter malfunction warnings at 39,000 miles, with the dealer declining service despite photographic evidence of the warning message. Owners also report harsh shifting, grinding and whining sounds, delayed shifts, and jerking motion, sometimes followed by a second transmission replacement that did not resolve the issue.
Recall campaign 22V746000 (transmission control software update) has been performed on multiple vehicles, yet owners report the failure recurred afterward. One owner reports the recall repair itself caused harsh shifting and activated a transmission code P1C2D03.
Beyond the transmission, owners describe engine misfire leading to fuel tank pressurization and backfiring that made the fuel tank expand so severely it popped the seat cushion up—the dealership deemed the vehicle unsafe. Coolant loss without visible leaks has also been reported, suspected by one owner to be a design flaw in the heater recirculation system. Dealers frequently cannot or will not reproduce these issues, and some refuse to honor recall coverage without active fault codes at the moment of scanning.
Same Hyundai Sonata powertrain reports on nearby years: 2018 · 2020 · 2022 · 2023
Failure modes owners describe
Transmission Control Unit (TCU) Software Failure & Recall Ineffectiveness
Owners report that TCU software updates performed as part of recall campaign 22V746000 did not resolve transmission control issues. Some vehicles exhibited the same failure modes after recall repair was completed.
When: Between 12,100 and 35,000 miles; recurring months to years after TCU update
Symptoms owners cite: Vehicle deceleration in fail-safe mode when accelerator depressed; Delayed acceleration response or complete loss of power; Vehicle failure to accelerate as needed; RPM fluctuations and uncontrollable RPM changes
Codes mentioned: 22V746000
Repairs/costs cited: TCU software update performed under recall; transmission replaced in some cases but issue recurred
Recalls/TSBs owners mention: Recall campaign 22V746000 issued; TCU software update remedy applied; some owners report recall repair did not resolve issue
Transmission Mechanical Failure & Replacement Ineffectiveness
Multiple owners report transmission failures requiring replacement, including cases where replacement did not resolve the underlying issue. Some failures occur shortly after previous transmission replacement under warranty.
When: 2,212 miles (warranty replacement); recurrence at 39,000 miles; cold start failures at approximately 2 years ownership; 28,000 miles; 2,700 miles
Symptoms owners cite: Grinding and whining sounds from transmission; Delayed shifts and jerking motion; Burning smell from vehicle vents; Popping and jerking on cold start with RPM increase but limited speed; Harsh shifting after recall service; Vehicle will not shift to neutral, drive, or reverse
Codes mentioned: P1C2D03
Repairs/costs cited: Transmission replaced under warranty at 2,212 miles; transmission replaced again with issue recurring 1 month after second replacement; transmission drain/flush performed but worsened condition in one case; owner cited $13,000 repair cost; transmission replacement after recall did not resolve failure
Recalls/TSBs owners mention: Transmission replaced under warranty; recall campaign 236 (Power Train) mentioned; manufacturer declined warranty repair in one case stating no active fault codes present despite photographic evidence of warning; manufacturer offered no assistance in some cases
Shifter System Malfunction & Dashboard Warning
Owners report shifter button malfunction with dashboard warning 'Shifter system malfunction! Service immediately.' This occurred on a vehicle that had already undergone a transmission replacement under warranty at low mileage.
When: At 39,000 miles; months after early transmission replacement at 2,212 miles
Symptoms owners cite: Shifter button would not function; Dashboard message 'Shifter system malfunction! Service immediately'; Loss of shifter responsiveness creating traffic safety risk
Repairs/costs cited: Vehicle rejected by dealer who cited lack of active fault codes despite photographic proof of warning message; no repair performed
Recalls/TSBs owners mention: Dealer declined warranty or recall repair; stated no diagnostic log history of transmission error code; owner reports vehicle is in scope for Hyundai advertised 8-Speed DCT Safety Recall for same year/make/model but VIN excluded from recall campaign
Engine Misfire with Fuel Tank Pressurization & Backfiring
Owners report engine misfiring with ignition coil replacement attempts, progressing to fuel tank pressurization issues causing backfiring and fuel tank expansion. One owner received notification of recall 25V796000 (fuel tank fire risk) but dealership refused to treat concern as recall-related.
When: Multiple visits over time; fuel tank pressurization issue discovered during diagnostic visit
Symptoms owners cite: Engine misfiring and check engine light; Two ignition coils replaced without resolving issue; Fuel dumping from vehicle; Backfiring sounds traced to fuel tank expanding; Fuel tank expansion causing seat to pop up; Reduced engine performance; Dealership deemed vehicle unsafe to drive
Codes mentioned: P14EE, 25V796000
Repairs/costs cited: Ignition coils replaced (two total); fuel system sensor replaced without owner authorization; vehicle deemed unsafe to drive
Recalls/TSBs owners mention: Recall 25V796000 (fuel tank pressurization and fire risk) applicable; dealership refused to treat as recall-related without diagnostic fee and attempted to reclassify as customer-pay fuel pump repair; dealership did not document recall inspection or provide test results ruling out recall condition
Loss of Motive Power & Fail-Safe Mode Activation
Owners report unexpected loss of motive power while driving at highway speeds, with the vehicle entering fail-safe mode. In one case, the vehicle would not shift gears after power loss event.
When: At 30-35 MPH and 65 MPH driving speeds; at 41,000 miles
Symptoms owners cite: Sudden loss of power for seconds then recovery; Vehicle deceleration when accelerator depressed; Vehicle would not shift to neutral, drive, or reverse; RPM fluctuations after initial power loss; Check engine warning light illuminated (in some cases); Knocking sound from vehicle (in one case); Loss of power with oil warning light illuminated (in one case)
Codes mentioned: 22V746000
Repairs/costs cited: Vehicle restarted and returned to normal in some instances; transmission and engine replacement recommended in one case but not performed; no repair in other cases
Recalls/TSBs owners mention: Manufacturer contacted in some cases; offered no assistance; case filed in one instance; some VINs not included in recall campaign 22V746000 despite similar symptoms
Coolant Loss with EHRS (Engine Heater Recirculation System) Suspected
Owner reports sudden coolant loss with no visible leak, low oil indicator, or temperature gauge warning. Issue suspected to be related to engine heater recirculation system design flaw.
When: In 30-degree weather; no mileage specified
Symptoms owners cite: Sudden loss of heat; No warning lights or temperature gauge indicators; Extremely low coolant level discovered; Rapid coolant loss despite no visible leak; Oil level remained normal (no consumption)
Repairs/costs cited: Owner purchased and added coolant; issue recurred shortly after
Synthesized from 21 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 4 most recent
Car transmission seemed to make a "clunking" sound when selecting gear from park. The car would not accelerate, the throttle seemed to be stuck and the transmission would try to downshift, but the car was not picking up speed. I eventually pulled off the road into a parking lot and turned the car off. I then restarted the car and it seemed to clear the problem, but no warning lights ever came on,…
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…
The contact owns a 2021 Hyundai Sonata. The contact stated that while driving at 30 MPH and depressing the accelerator pedal, the vehicle failed to respond and lost power. The vehicle was coasted over to the right side of the road, turned off, restarted, and returned to normal functionality. An independent mechanic was contacted. The vehicle was taken to an independent mechanic to be diagnosed;…
Had powertrain trouble with your 2021 Hyundai Sonata?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the powertrain problem on the 2021 Hyundai Sonata?
It's a documented issue but not catastrophic. 21 complaints have been filed. Repairs average $2,500 and most owners catch it before it causes a breakdown.
At what mileage does the powertrain typically fail?
Based on the 21 complaints filed, powertrain issues most often appear around 22,300 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
What does it cost to fix?
Independent shops typically charge around $2,500 for powertrain repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to powertrain?
No active recalls currently cover powertrain issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2021/Hyundai/Sonata.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.