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 ↗2018 Hyundai Sonata electrical problems
severe Owners of the 2018 Hyundai Sonata have filed 51 NHTSA complaints about the electrical, typically surfacing around 20,500 miles at roughly $850 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See electrical across all vehicles →
Failure mileage
Complaints
51
Recalls
0
Avg fix
$850
| Model year | electrical complaints |
|---|---|
| 2014 Sonata | 113 |
| 2015 Sonata | 141 |
| 2016 Sonata | 73 |
| 2017 Sonata | 46 |
| 2018 Sonata (this page) | 51 |
| 2019 Sonata | 11 |
| 2020 Sonata | 26 |
| 2021 Sonata | 14 |
| 2022 Sonata | 12 |
1crash
3fires
1injury
When does it fail?
Of the 51 electrical complaints filed for the 2018 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.
What stands out
Owners have filed 51 electrical 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 electrical 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 ↗Some vehicles may exhibit difficulty starting in cold weather. This bulletin provides the procedure to perform an inspection on the starter magnetic switch for potential freezing and, if necessary, replace the starter magnetic switch (solenoid) assembly.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The 2018 Sonata electrical system shows a pattern of multiple distinct failures. The most common and dangerous is the knock-sensor limp-mode event: without warning, the engine loses power on the highway, flashing check engine light, and the car can only creep to 20–60 mph. This has nearly caused rear-end collisions. Dealers replace wiring harnesses, reprogram the computer, clean or swap knock sensors—yet it happens again. Code P1326 keeps coming back. The turbo 2.0L GDI engine burns oil relentlessly, requiring top-ups every 1,500–2,000 miles or more, with no visible leak. Eventually the engine seizes. Hyundai denies warranty unless you have every oil-change receipt (one owner's were stolen), then makes you pay $600–$850 for combustion tests before approving a $14,000 engine swap.
Cold weather below 20–50°F triggers starter failure: dash lights work, but the motor won't crank. Battery tests fine. It starts when warm. The starter eventually burns out with sparks and burning-wire smell. Brake systems fail suddenly—no stopping power, ABS grinds, automatic emergency braking doesn't engage—yet swapping the ABS module doesn't fix it. Infotainment freezes and static fills the speakers. Electrical shorts have caused fires in the engine bay, with melted batteries and no clear root cause identified. One collision happened when brakes simply did not respond. Dealerships either cannot diagnose these issues or blame owners for missing service records, offering little help within warranty periods.
Same Hyundai Sonata electrical reports on nearby years: 2015 · 2016 · 2017 · 2019 · 2020
Failure modes owners describe
Knock Sensor / Engine Control System Limp Mode
Engine enters limp mode with flashing check engine light and code P1326 (knock sensor) or similar engine control faults. Vehicle loses power, cannot accelerate above 20-60 mph, jerks, and shudders. Often triggered after software updates or during normal driving. Repeated failures even after wiring harness replacement, knock sensor cleaning/replacement, and ECM resets. Multiple dealers unable to resolve persistent recurrence.
When: 10k–70k miles; often shortly after software recall updates
Symptoms owners cite: Flashing check engine light; Sudden loss of power and acceleration; Vehicle enters limp mode (max 20–60 mph); Engine jerking and shuddering; Code P1326 or similar engine control codes; No warning before power loss on highway
Codes mentioned: P1326, Code 1326, P0606, C1741, C2402, C1360
Repairs/costs cited: Wiring harness replacement, knock sensor replacement/cleaning, ECM/computer reset and software updates, engine replacement (in severe cases). Costs cited: $175–$1,500+ for diagnostics and parts; full engine replacement $14,000+. Parts often on backorder for months.
Recalls/TSBs owners mention: Hyundai Bearing Clearance Test (paid by owner, ~$350); ECU KSD logic upgrade required (~$175); knock sensor software recall update; 120k-mile warranty extension on knock sensor systems. No official recall issued despite widespread pattern.
Excessive Oil Consumption and GDI Engine Failure
Turbo 2.0L GDI engines consume oil rapidly, requiring top-ups every 1,500–2,000 miles or even more frequently. Oil becomes black and low between services with no visible external leak. Owners report the engine eventually seizing, requiring replacement. Dealerships initially deny warranty coverage, cite missing oil-change receipts, or require multiple expensive diagnostic tests (combustion chamber tests ~$600–$850) before approving engine replacement. Pattern suggests known defect in GDI fuel injection system.
When: 48k–125k miles; can manifest early (under 20k) and worsen over time
Symptoms owners cite: Oil burns rapidly with no visible leak; Oil change light comes on every 1,500–2,000 miles; Oil appears black and low between services; Engine clanking, knocking, or sputtering under acceleration; Limp mode at higher mileage; Engine seizes if not caught early
Repairs/costs cited: Multiple diagnostic tests required (combustion chamber cleaning $600–$850, oil consumption testing). Engine replacement $14,000+ (not always covered under warranty). Owners cite lack of oil-change receipts (especially if vehicle was stolen) as dealership grounds for warranty denial. One owner reports dealership holding vehicle 300+ days without resolution.
Recalls/TSBs owners mention: Hyundai initially denies warranty on excessive oil consumption without complete service history. May offer engine replacement if combustion test confirms internal failure. No formal TSB or recall issued; pattern appears known internally but handled case-by-case.
No-Start / Cold-Weather Starter Failure
Vehicle fails to start or cranks very slowly when ambient temperature drops below 20–50°F. Dash lights illuminate normally, but starter does not engage (no click, no crank). Battery and alternator test normal. Condition recurs after warming. At higher mileage, starter solenoid or starter motor fails and burns out, creating burning-wire smell and smoke from engine bay. May occur without warning lights.
When: 6k–72k miles; cold-weather events; also random no-crank at any temperature
Symptoms owners cite: Failure to start in cold weather (below 20–50°F); No click or crank sound from starter; Dash lights illuminate normally; Vehicle starts fine when warmed to 40–50°F; Starter burns out abruptly with burning-wire odor and smoke; Immobilizer light may appear intermittently
Repairs/costs cited: Starter replacement $300–$500+ labor and parts (one owner paid $492 for parts and labor). Battery replacement ($300) does not resolve cold-start issue. Warranty expires at 5 years or 60k miles; many owners denied coverage due to age or mileage despite known pattern.
Recalls/TSBs owners mention: No recall issued. Dealers unable to diagnose or replicate in warmer weather. One owner reports dealer could not locate issue and extended service appointments. Some independent shops identify problem correctly; dealerships do not.
Brake System and ABS Electrical Faults
Brakes fail suddenly or stutter during normal driving or emergency stops. Vehicle shakes and grinds. ABS activates inappropriately or does not function. Automatic emergency braking (AEB) system fails to engage. Multiple dashboard lights flicker or go out (speedometer, wheel-speed sensors, traction control, etc.). One case involved a collision when brakes did not respond; another noted a melted battery suggesting electrical short.
When: 4.7k–71k miles; failure can occur without warning
Symptoms owners cite: Brakes don't work or stutter during stops; Vehicle shakes and grinds during braking; ABS light and warning lights illuminate; Automatic emergency braking fails to engage; Speedometer, fuel gauge, and sensor lights flicker or go out; Traction control disables unexpectedly
Codes mentioned: C1741, C2402, C1360
Repairs/costs cited: ABS hydraulic module replaced; new units exhibit same failure. TSB 18-BR-001 referenced by one dealer but no permanent fix provided. One owner replaced ABS module, but replacement failed identically. Electrical root cause not diagnosed.
Recalls/TSBs owners mention: TSB 18-BR-001 exists but dealers state no warranty or corrective action available. One owner reported manufacturer stated nothing could be done.
Electrical System and Dashboard Faults
Interior and exterior lighting malfunction intermittently. Headlamps, interior dome lights, running lights, and tail lights fail to activate when expected. Infotainment system (touchscreen, Apple CarPlay, audio) freezes, displays static, or resets. Charging system warning lights appear without clear cause. One case involved a melted battery in a collision context, suggesting possible electrical shorts or over-charging.
When: 20k–125k miles; often intermittent and temperature-dependent
Symptoms owners cite: Headlights or dome lights fail to turn on; Tail lights or running lights burn out prematurely; Infotainment screen freezes or displays static; Apple CarPlay/Siri malfunction and cut out; Charging system warning light illuminates; Multiple dashboard lights flicker or go out simultaneously
Repairs/costs cited: Dealership offers interior light replacement but notes that is unlikely the root issue. One owner replaced multiple light assemblies with no resolution. Infotainment issues persist despite software resets and new cables.
Recalls/TSBs owners mention: Dealers diagnose component-level failures (bulbs, modules) but do not address underlying electrical harness or charging system faults. No TSBs or recalls issued for pattern electrical issues.
Engine Fire and Thermal Runaway
Vehicle catches fire in engine compartment, sometimes unprovoked while parked or during normal driving. Brown smoke and flames reported. One case involved a melted battery and melted surrounding plastic/rubber components, suggesting electrical short or thermal runaway. Another involved a starter short causing sparks. Fire departments unable to determine exact electrical cause.
When: 125k miles and unknown mileage; one incident during startup attempt
Symptoms owners cite: Brown or black smoke from engine bay; Vehicle engulfed in flames minutes after smoke observed; Burned smell from engine; Melted battery case; Melted adjacent plastic and rubber components
Repairs/costs cited: Vehicle deemed total loss by insurance in one case. Towed and salvaged.
Recalls/TSBs owners mention: Manufacturer not notified in one case; no recall or warning issued. Fire cause labeled 'electrical' but exact component not identified.
Trunk Latch Failure
Trunk latch fails, rendering trunk stuck closed or stuck open. After dealership service on a trunk recall, trunk became stuck and difficult to open/close. Trunk pops open randomly while driving. Emergency cable associated with latch requires replacement.
When: 44k miles and during/after recall service
Symptoms owners cite: Trunk stuck closed and difficult to open; Trunk pops open during driving; Cannot open trunk with key fob or interior control; Trunk will not stay closed; Problem worsened after dealership recall service
Repairs/costs cited: Trunk latch and emergency cable replacement required. One case: issue created during recall service and not resolved by dealership.
Recalls/TSBs owners mention: Recall TSB performed but created new problem; dealership gave vague appointment timeline, suggesting low priority.
Synthesized from 51 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 5 most recent
Intermittent no-crank, no-start condition. Dash lights illuminate, push-button start produces no response. Brake pedal applied. Vehicle becomes immobilized without warning. I’ve been stranded on multiple occasions. Unable to commute to work, or home. Most recently on December 19,2025 the car completely shut off while driving on the highway.
We were heading to Lakewood NJ from Bucks County (North of Philly) . Car trouble w/ hybrid system on Rt 1, just past I-95. Got off @ Fairless Hills & took back roads. We could only go 20-30 mph. IDK how many times I pulled over. Several lights on, including "Check hybrid system. Turn Engine off", engine light, low tire pressure, battery & 3 other unidentifiable lights. I turned around to try…
My 2018 sonata will not start when temp drops below 20 deg f. It has happened 3 times this winter and when it warms back up to 40 to 50 degree it will start. When I turn the key on all the lights on the dash light up like normal. I can move hear selector and turn wheel. But the starter will not engage nothing is heard not a click or a shirt. Is this common problem?
Entertainment screen turns off after a while and will reset or I have to tap it and make sure it goes back on and does this over and over at times. Smoke comes out exhaust when passing a car sometimes
The contact owns a 2018 Hyundai Sonata. The contact stated that the vehicle failed to start in cold weather, below 50 degrees Fahrenheit. The contact stated that the vehicle would start as needed whenever the weather was warmer. The vehicle was taken to an independent mechanic, where it was diagnosed; however, the cause of the failure could not be determined. The dealer was notified of the…
Had electrical trouble with your 2018 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 electrical problem on the 2018 Hyundai Sonata?
It's a meaningful issue. 51 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $850.
At what mileage does the electrical typically fail?
Across the 25 complaints that reported odometer mileage, most electrical failures cluster between 11,000 and 51,160 miles, with the median around 20,500. A quarter of owners report trouble before 11,000; a quarter make it past 51,160. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
What does it cost to fix?
Independent shops typically charge around $850 for electrical 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 electrical?
No active recalls currently cover electrical 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/2018/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.