Certain Santa Fe (TMA), Santa Fe Sport (AN), Sonata (LFA), and Tucson (TL) vehicles equipped with Theta II engines may exhibit elevated engine-out emissions. This bulletin provides instructions for updating the Engine Control Module (ECM) to address this condition.
full bulletin at NHTSA ↗2020 Hyundai Tucson engine problems
moderate Owners of the 2020 Hyundai Tucson have filed 55 NHTSA complaints about the engine at roughly $3,100 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See engine across all vehicles →
Complaints
55
Recalls
0
Avg fix
$3,100
| Model year | engine complaints |
|---|---|
| 2016 Tucson | 236 |
| 2017 Tucson | 435 |
| 2018 Tucson | 157 |
| 2019 Tucson | 133 |
| 2020 Tucson (this page) | 55 |
| 2021 Tucson | 29 |
| 2022 Tucson | 55 |
| 2023 Tucson | 8 |
| 2024 Tucson | 8 |
What stands out
Engine accounts for 32% of every owner complaint on file for this vehicle — the dominant problem area across 8 categories tracked.
Owners have filed 55 engine complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering engine on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
Certain Santa Fe (TMA), Santa Fe Sport (AN), Sonata (LFA), and Tucson (TL) vehicles equipped with Theta II engines may exhibit elevated engine-out emissions. The California Air Resources Board has determined that these vehicles may be releasing air pollutants which exceed Federal and California standards.
full bulletin at NHTSA ↗Following completion of Service Campaign 9C2 (Theta II Emissions Improvement), certain vehicles may exhibit a brief hesitation or rough shifting condition during cold start operation. If present, this condition is expected to occur only within approximately the first 1-3 minutes after engine start, while the catalyst is reaching its normal operating temperature.
full bulletin at NHTSA ↗Following completion of Service Campaign 9C2 (Theta II Emissions Improvement), certain vehicles may exhibit a brief hesitation or rough shifting condition during cold start operation. If present, this condition is expected to occur only within approximately the first 1-3 minutes after engine start, while the catalyst is reaching its normal operating temperature.
full bulletin at NHTSA ↗Certain 2019 – 2020 model year Santa Fe, 2017 – 2018 model year Santa Fe Sport, 2015 – 2019 model year Sonata, and 2018 – 2021 model year Tucson vehicles may exhibit elevated engine-out emissions. Hyundai is conducting a service campaign to update the Engine Control Module (ECM) Software for vehicles equipped with the (2.4 GDI) Theta II engine to improve engine combustion and fuel trim adaptations.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The 2020 Tucson engine fails across two primary failure patterns that Hyundai service advisors themselves acknowledge as recurring problems on these vehicles.
Oil consumption and starvation: Owners report burning 1 to 4+ quarts between scheduled 5,000–6,000 mile oil changes, with some vehicles consuming a quart every 150–900 miles. Despite no visible leaks, oil levels plummet between services. More troubling: the low-oil warning light does not stay on—it flickers briefly during hard braking or sharp turns, then resets, making it easy to miss until the engine is critically low. Hyundai's response is a 1,000-mile oil-consumption test. If the engine burns more than 1 quart per 1,000 miles, dealerships offer combustion chamber cleaning (owners report this does nothing) or eventually engine replacement. Second owners have been denied even the cleaning procedure.
Catastrophic engine failure with no warning: Multiple owners describe sudden engine shutdown at highway speed, with check-engine and oil lights appearing only *after* the engine has already failed or begun rattling. One owner had the engine seized after a drain plug disappeared during normal driving, 1,265 miles post-service at a Hyundai dealer; another owner's engine failed at 89,000 miles with the same missing-plug scenario. Service advisors confirm they've seen drain plugs back out during highway driving. Hyundai denies warranty coverage for these events, claiming the customer is responsible.
Owners also report repeated check-engine light cycles (limp mode, reduced speed to 40–50 mph) after knock sensor replacement and carbon cleaning—issues that recur within weeks.
Same Hyundai Tucson engine reports on nearby years: 2017 · 2018 · 2019 · 2021 · 2022
Failure modes owners describe
Excessive oil consumption (internal breakdown)
Engine burning through 1–4+ quarts between routine oil changes or per 1,000 miles, no visible external leak, typically no illuminated low-oil warning until levels drop critically. Owners report needing to top off every 1,000–6,000 miles; some consume a quart every 150–900 miles. No low-oil gauge light that stays on; only a flickering pressure light that briefly illuminates during hard braking or turns, easily missed.
When: Begins around 37,000–80,000 miles; some reports from near new. Often discovered at routine oil changes or when owners check dipstick proactively.
Symptoms owners cite: Engine burning oil at rates well above normal (1+ qt/1000 mi); No visible oil leaks on driveway or under hood; Check engine light may illuminate; Flashing or brief low-oil pressure light that resets; Engine running rough, sputtering, shaking in some cases; Burnt smell, smoke from engine or exhaust in advanced cases; No persistent warning light to alert driver of low level
Codes mentioned: P0420 (catalytic converter deficiency, secondary to oil consumption)
Repairs/costs cited: Hyundai dealership protocol involves 1,000-mile oil consumption test; if consumption >1 qt/1000 mi, combustion chamber cleaning offered (owners report this does not resolve issue). Engine replacement ultimately required. Second-owner vehicles reportedly denied coverage for combustion cleaning. Costs mentioned: engine replacement $3,000–$5,000+ out-of-pocket.
Recalls/TSBs owners mention: Hyundai acknowledged as 'known issue' by multiple service advisors. Company operates multi-step diagnostic protocol (1,000-mile checks) but denies some owners coverage based on ownership status. No large-scale recall observed in complaints; extended warranty denial cited.
Oil drain plug disappearance or failure
Oil drain plug (installed during dealer service) becomes loose or completely falls out while driving, resulting in rapid oil loss, low/no oil condition, and catastrophic engine damage (blown or seized engine). Occurs shortly after oil changes at dealership. Owner reports initial misdiagnosis as 'hole in engine', later corrected to missing plug.
When: Within 1,265–1,500 miles post-oil-change service at dealership. Can remain partially loose during low-speed city driving, then suddenly back out on highway at higher RPM.
Symptoms owners cite: White smoke from exhaust and engine while driving; Sudden loss of acceleration; Engine and oil light illuminate after smoke appears; Complete engine shutdown with no prior warning lights; No oil on dipstick; Engine locked, seized, or blown
Repairs/costs cited: Dealership initially diagnosed as 'hole in engine'; later revealed to be missing drain plug. Engine required replacement. Owner cited the dealership's own service advisor noting that an improperly torqued plug could gradually work loose during short, low-speed trips, then fully back out during highway acceleration.
Recalls/TSBs owners mention: Hyundai declined warranty coverage, stating it is 'owner's problem'. Insurance denied coverage as well. No TSB or recall mentioned. One service advisor acknowledged seeing this issue before on these vehicles.
Engine knock / bearing failure / foreign material
Engine develops loud internal knocking or rattling, often accompanied by loss of power or reduced acceleration, leading to diagnosis of failed crankshaft bearing or knock sensor failure. Some cases traced to foreign material in the engine or depletion of oil (secondary to consumption). Engine seizes or requires replacement.
When: Mileage ranges 79,000–122,000 miles. Can occur suddenly without prior warning or follow a pattern of check engine light cycling.
Symptoms owners cite: Loud, abnormal knocking or rattling from engine; Vehicle unable to accelerate past 40–50 mph or loses power suddenly; Car shaking or hesitating; Check engine light flashing or solid; Oil light briefly illuminates; Engine starting, slowing down, or seizing
Codes mentioned: Knock sensor failure (initial misdiagnosis in some cases), Crankshaft bearing failure (confirmed diagnosis)
Repairs/costs cited: Some cases initially diagnosed as knock sensor failure; replacement of sensor did not resolve underlying engine failure. One independent mechanic diagnosed 'defect in one of the engine cylinders.' Engine replacement required. One owner reported diagnostic cost ~$400 for investigation.
Recalls/TSBs owners mention: No widespread recall cited. Dealerships unable to replicate intermittent issues in some cases; investigations sometimes inconclusive or delayed.
Catalytic converter failure / clogging (secondary to oil consumption)
Catalytic converter fails or becomes clogged, triggering P0420 diagnostic code and check engine light. Multiple reports suggest this occurs secondary to excessive oil consumption; carbon/sludge buildup from burning oil fouls the converter. Replaced on warranty or out-of-pocket at low mileage (37,000–80,000 miles).
When: Appears between oil changes or after sustained high oil-consumption period. Reported at 37,000–77,000+ miles.
Symptoms owners cite: Check engine light (solid or flashing); Reduced acceleration or hesitation; Potential rotten-egg smell from exhaust (sulfur/cat converter)
Codes mentioned: P0420 (catalyst system efficiency below threshold, Bank 1)
Repairs/costs cited: Catalytic converter replaced under warranty at low mileage or out-of-pocket. One owner reported second failure at 77,000 miles after first replacement at 52,000 miles. Combustion chamber cleaning performed in some cases before or alongside converter replacement.
Recalls/TSBs owners mention: Replacement covered under warranty (at least for initial occurrence). 2019 Tucson 2.0-liter engines had a recall for exhaust manifold/catalyst sensor; not confirmed as applied to 2020 2.4-liter models.
Engine failure / seizure with no warning
Engine shuts down suddenly with little or no prior warning, often on highway at speed, causing loss of control and safety hazard. Vehicle cannot be restarted. Towing and diagnosis reveal blown, seized, or locked engine requiring complete replacement. Root cause typically traced to oil starvation (low/missing oil from consumption or drain plug loss).
When: Mileage varies 32,000–122,000 miles. Can occur on first major highway drive after service or after prolonged high oil consumption.
Symptoms owners cite: Sudden loss of power at cruise speed; Engine begins loud rattling or knocking moments before shutdown; Check engine, oil, battery, or dashboard lights illuminate (usually only after failure); Vehicle coasts to a stop and will not restart; No oil or dangerously low oil on dipstick
Repairs/costs cited: Engine replacement required. Estimated cost $3,000–$5,000+ out-of-pocket depending on warranty status and ownership. Multiple owners report no prior warning lights and clear maintenance history.
Recalls/TSBs owners mention: Warranty denial common, citing oil consumption as 'owner maintenance issue' or drain plug loss as 'not a defect.' Some cases referred to insurance, which denied coverage. One owner cited an open NHTSA investigation into this exact issue.
Check engine light with limp-mode / deceleration (carbon/sensor issues)
Check engine light illuminates repeatedly, triggering limp mode (reduced speed to 40–50 mph) and hesitation/lurching. Dealership replaces knock sensor, cleans carbon, or updates ECM software; issue recurs within days to weeks. Vehicle unsafe at highway speeds.
When: Intermittent; occurs 2–3+ times over months. First incident often 2.5 months into ownership or after first carbon cleaning.
Symptoms owners cite: Check engine light (solid or flashing); Vehicle limited to 40–50 mph, will not accelerate further; Car lurching, hesitating, or jerking forward; No prior mechanical noise or smoke; Symptoms recur after service despite repair attempts
Codes mentioned: Check engine light (specific code not always stated)
Repairs/costs cited: Knock sensor replacement (unsuccessful in repeat cases). Carbon combustion chamber cleaning performed 2–3 times with temporary relief (2 weeks to 2 months). ECM software update performed in at least one case. Dealership unable to replicate issue reliably, leaving root cause unresolved.
Recalls/TSBs owners mention: Dealership repeats same procedures (cleaning, sensor swap) without identifying underlying defect. No TSB or recall documented in complaints for this issue.
Synthesized from 55 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 3 most recent
Engine light was flashing on and off in September 2022 I took it in to a Hyundai dealer in September and was told it was the Catalytic convertor. The catalytic convertor was replaced in October 2022, 2 weeks later the engine light was flashing and the car would not accelerate. I took the care that day to Freehold Hyundai where after keeping it for 3 days they said it was an issue with the oil…
While driving down the interstate to go back to my college, I noticed a cloud of white smoke coming out of my exhaust. Seconds later, I no longer could accelerate and white smoke was also coming out of the engine. There were no lights on my dash at this point or at any point before this day. I quickly tried to get off of the road when I noticed my car was no longer going. I managed to get to the…
Vehicle excessively burns oil, engine drives rough, exhaust developed smoke, burnt smell in engine, engine and oil gauge light comes on.
Had engine trouble with your 2020 Hyundai Tucson?
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 engine problem on the 2020 Hyundai Tucson?
It's a documented issue but not catastrophic. 55 complaints have been filed. Repairs average $3,100 and most owners catch it before it causes a breakdown.
At what mileage does the engine typically fail?
Based on the 55 complaints filed, engine issues most often appear around 94,674 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 $3,100 for engine 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 engine?
No active recalls currently cover engine 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/2020/Hyundai/Tucson.
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.