2021 Hyundai Sonata: Engine complaints
Owner-reported issue (NHTSA complaints, not a recall)
Symptoms
NHTSA has 35 owner complaints for the 2021 Hyundai Sonata that list the engine component. Complaints are individual owner reports, not verified defects.
Examples:
- NHTSA complaint ODI #11754136 (filed 08/01/2026): “Going down the road driving the car lost power and went in limp mode with no warnings on the dash at all!…”
- NHTSA complaint ODI #11746137 (filed 06/24/2026): “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…”
- NHTSA complaint ODI #11741201 (filed 06/01/2026): “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…”
Likely causes
These complaints do not establish a single root cause; read the examples above and get a diagnosis.
Fix, in plain English
No single fix is established by these reports. Check your VIN for open recalls at nhtsa.gov/recalls, ask a dealer about technical service bulletins (TSBs) or extended warranty coverage, then have the system diagnosed.
DIY difficulty: Pro
Internal engine work (lifters, oil consumption, fuel dilution diagnosis) requires engine teardown or dealer software/tests. (Our assessment.)
Cost
No sourced cost range for this issue. Get a written quote after diagnosis.
Typical parts (search links, no affiliate codes)
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Sources
Page last updated .