Free used car buyer guide / JF fourth generation / 2017-2020
Kia Optima common problems and best years
By BYBA Research - how we score cars
Updated 2026-06-12
BYBA Buy Score
6.0/10
2 walk-away risks, 5 serious faults, 1 minor fault documented for this generation, weighted by severity and repair cost. Biggest factor: theta ii rod-bearing knock / engine seizure campaign exposure. Score methodology.
The 2017-2020 Optima can be cheap, comfortable transport, but only when the engine-recall and theft questions are settled before purchase. The expensive risks are Theta II bearing failure/knock, fire-related ABS/HECU recalls, fuel leaks, keyed-car theft damage, turbo oil/cooling neglect, hybrid/PHEV battery or charge faults, and panoramic roof/body-electrical issues. Best buy is a push-button-start 2019-2020 2.4 or 1.6T with Kia campaign proof, clean knock-sensor software history, and no oil-use/engine-noise story.
Faults covered
8
Highest risk
Theta II rod-bearing knock
Best years
2019-2020
Best buys
- 2019-2020 push-button-start car with complete recalls and clean engine scan.
- 1.6T/7DCT only if creep is smooth and service records are strong.
- Hybrid/PHEV only after battery/charge scan and warranty proof.
Inspect hard
- 2017-2018 2.4/2.0T for Theta II campaign history, oil use, and prior engine replacement.
- Keyed ignition cars for insurance, theft repair, and Kia anti-theft update.
Avoid
- Any Optima with knock, oil pressure warning, metal in oil, or vague "new engine" claim.
- Turbo car with smoke, low boost, or coolant/oil leaks.
Next checks
Before you contact the seller
Check the car's history first. Then bring the right tools if it still looks worth viewing.
Primary next step
Check history, title, and recall status
The faults above matter more if the car also has accident history, finance flags, missing service records, or open safety recalls.
Viewing kit
Bring the right tools
Four cheap tools catch most of the faults on this page at a Kia Optima viewing.
Printable workflow
Take the inspection pack
The PDF is the ordered checklist for the viewing: documents, walk-around, test drive, and scan.
Open PDF optionSome links here are partner links. If you buy through one, BYBA earns a commission. The price you pay does not change. How we make money.
Engines and trims
Which Kia Optima should you buy?
On most used cars, the engine and trim choice changes the risk more than the mileage does. Narrow this down before you start viewing cars.
2.4 GDI Theta II
2017-2020
RECALL PAPERWORK DECIDES IT
Comfortable and common, but rod-bearing history and knock-sensor campaign status are the purchase gate.
2.0T GDI Theta II
2017-2020 SX
FAST BUT HIGHER RISK
Adds turbo heat and higher repair costs to the same family of engine-risk questions.
1.6T with 7-speed DCT
2017-2020 LX/EX by market
ECONOMICAL IF DCT IS SMOOTH
Avoids some Theta II concerns but brings dry-clutch behaviour and turbo service sensitivity.
Hybrid / Plug-in Hybrid
2017-2020
BUY ONLY AFTER HYBRID SCAN
Efficient, but battery, charger, inverter and cooling faults are specialist inspections.
Year notes
Year-by-year buyer advice
Use this to narrow the search before you spend time travelling to view a car.
2017
JF continues; hybrid/PHEV available.
Buyer: Check Theta II, hybrid, and theft/insurance exposure before price.
Owner: Keep campaign documents with engine-service records.
2018
Similar range; recall population remains important.
Buyer: Prior engine replacement is acceptable only with Kia invoice and warranty status.
Owner: Oil-level checks matter between services.
2019
Facelift and renamed trims in many markets.
Buyer: One of the better years if recall/theft status is clean.
Owner: Keep software and anti-theft updates documented.
2020
Final Optima year before K5 replacement.
Buyer: Best late target, but do not skip engine and fire-recall lookups.
Owner: Resolve open campaigns before selling.
Common problems
Faults to check before buying
What fails, what it looks like, what it costs, and the quick checks you can do at the viewing - ranked by how badly each one can hurt you.
Fault 1
Theta II rod-bearing knock / engine seizure campaign exposure
Affects
2017-2020 2.4 GDI and 2.0T populations; VIN status matters.
Symptoms
Knock, limp mode, flashing MIL, oil pressure warning, engine replacement record.
Typical repair cost
USD 0 campaign if approved; USD 5,000-9,000+ engine outside coverage.
Codes / scan clues
P1326 knock-sensor logic, misfire/oil-pressure codes.
Root cause: Bearing wear/debris/oil starvation issues in Theta II family can lead to seizure.
Quick check
- Run VIN through Kia and NHTSA recall/campaign lookup.
- Cold start and listen for lower-end knock.
- Scan for P1326 and cleared/previous engine codes.
- Verify any replacement engine with Kia paperwork and warranty.
Fault 2
ABS/HECU electrical short and engine-bay fire recall
Affects
Optima recall populations by year/VIN.
Symptoms
Open recall, ABS light, burning smell, battery drain, fire damage.
Typical repair cost
USD 0 recall; USD 800-2,500 ABS module/wiring if outside campaign.
Codes / scan clues
ABS/ESC/module communication codes.
Root cause: Hydraulic electronic control unit can short internally and create fire risk.
Quick check
- Run VIN for open Kia fire/ABS recalls.
- Inspect engine-bay fuse/ABS area for heat marks or replaced wiring.
- Confirm fuse/HECU recall remedy invoice.
- Avoid cars with unexplained electrical smell or fire title.
Fault 3
Keyed-ignition theft vulnerability and poor repairs
Affects
Key-start US Optima trims without immobilizer.
Symptoms
Theft claim, broken steering column, no insurance quote, body-control faults.
Typical repair cost
USD 0 campaign if eligible; USD 600-2,500+ theft repair.
Codes / scan clues
BCM, airbag, immobilizer and steering-column codes.
Root cause: Keyed Kia/Hyundai theft method damages ignition/column and raises insurance risk.
Quick check
- Confirm push-button start or immobilizer status.
- Get insurance quote before deposit.
- Inspect column trim, ignition, and under-dash wiring.
- Verify Kia anti-theft update and any theft repair invoices.
Fault 4
1.6T dry DCT shudder or delayed engagement
Affects
1.6T Optima with 7-speed DCT.
Symptoms
Shudder from stop, hesitation, clutch smell, harsh low-speed shifts.
Typical repair cost
USD 250-700 adaptation/software; USD 1,500-3,500 clutch/actuator.
Codes / scan clues
P17xx clutch/adaptation codes possible.
Root cause: Dry-clutch wear, heat, or actuator calibration issues.
Quick check
- Drive stop-start traffic until fully warm.
- Reverse uphill or into a parking space.
- Scan transmission module for clutch/adaptation history.
- Ask for DCT service or software update records.
Fault 5
2.0T turbo oil leak, smoke, or boost-control fault
Affects
2017-2020 SX/2.0T.
Symptoms
Blue smoke, oil smell, low boost, rattling wastegate, coolant/oil seepage.
Typical repair cost
USD 600-1,500 lines/diagnosis; USD 1,800-3,800 turbo replacement.
Codes / scan clues
P0299, boost control, misfire, catalyst codes.
Root cause: Heat, oil-feed/cooling neglect, PCV issues, or worn turbo/wastegate hardware.
Quick check
- Inspect turbo oil/coolant lines and undertray.
- Accelerate hard once warm and watch boost/smoke.
- Scan for underboost and misfire history.
- Avoid modified cars without tune/supporting paperwork.
Fault 6
Hybrid/PHEV battery, inverter, or charger fault
Affects
2017-2020 Optima Hybrid/PHEV.
Symptoms
Low EV range, charge fault, hybrid warning, poor fuel economy, no EV mode.
Typical repair cost
USD 300-1,000 diagnosis/minor; USD 2,000-5,000 inverter/OBC; battery warranty case if pack.
Codes / scan clues
BMS, inverter, OBC, isolation and cooling codes.
Root cause: HV battery ageing, charging hardware, cooling or inverter control faults.
Quick check
- Charge PHEV during viewing and confirm EV mode.
- Scan BMS/inverter/OBC modules.
- Verify hybrid warranty transfer and dealer service history.
- Check coolant loops and battery fan operation.
Fault 7
Panoramic sunroof rattle, leak, or glass mechanism fault
Affects
Higher-trim 2017-2020 Optima.
Symptoms
Roof rattle, water stains, slow shade, wind noise, drain blockage.
Typical repair cost
USD 150-500 drain/service; USD 1,000-2,500 cassette/glass work.
Codes / scan clues
Body module/sunroof codes possible.
Root cause: Track wear, blocked drains, poor adjustment, or impact damage.
Quick check
- Open/close roof and shade fully.
- Inspect headliner, A-pillars, and spare-wheel well for moisture.
- Drive over rough road and listen above front seats.
- Check for glass replacement or sealant evidence.
Fault 8
Fuel line, HPFP, or evap leak complaints
Affects
2017-2020 GDI/turbo cars; recall/TSB exposure varies.
Symptoms
Fuel smell, hard start, lean codes, evap codes, visible dampness near rail/lines.
Typical repair cost
USD 200-700 evap/sensor; USD 800-1,800 HPFP/line work.
Codes / scan clues
P0455, P0456, P0171, fuel-pressure codes.
Root cause: GDI high-pressure fuel hardware, fittings, purge/evap faults, or prior repair error.
Quick check
- Smell around engine bay and rear tank area after hot soak.
- Scan for evap and fuel-pressure codes.
- Inspect fuel-rail/HPFP area on turbo cars.
- Treat fuel smell as a no-buy until diagnosed.
Inspection pack
Printable checklist for the viewing
The free page helps you decide whether the car is worth seeing. The paid guide is the ordered, printable checklist you use at the car.
- VIN recall check for Kia Optima 2017-2020.
- Service invoices matching the engine/drivetrain and mileage, not only stamped history.
- Inspect tyres, leaks, accident repair and water entry before the test drive.
- Look specifically for evidence related to Theta II rod-bearing knock / engine seizure campaign exposure.
- Check every warning light, infotainment function, climate mode, camera/sensor warning and battery condition before moving.
- Cold start, full warm-up, low-speed manoeuvres and motorway-speed pull for Kia Optima.
- Recheck for smells, warning lights, harsh shifts, vibration or coolant/oil leaks after the drive.
- Scan engine, transmission, ABS/body and driver-assist modules where fitted.
- Treat cleared codes or incomplete readiness monitors as negotiation or walk-away evidence.
Bottom line
Buy: 2019-2020 push-button-start car with complete recalls and clean engine scan. 1.6T/7DCT only if creep is smooth and service records are strong.
Avoid: Any Optima with knock, oil pressure warning, metal in oil, or vague "new engine" claim. Turbo car with smoke, low boost, or coolant/oil leaks.
Quick answers
Kia Optima buyer questions
The short versions of what this page answers in full.
What are the most common Kia Optima 2017-2020 problems?
The highest-impact documented faults are: Theta II rod-bearing knock / engine seizure campaign exposure; ABS/HECU electrical short and engine-bay fire recall; Keyed-ignition theft vulnerability and poor repairs. This guide covers 8 faults in total, each with symptoms, typical repair costs, and checks you can do at a viewing.
Which Kia Optima years are the best to buy?
2019-2020 stand out in this generation. 2019-2020 push-button-start car with complete recalls and clean engine scan. 1.6T/7DCT only if creep is smooth and service records are strong.
Which Kia Optima should I avoid?
Any Optima with knock, oil pressure warning, metal in oil, or vague "new engine" claim. Turbo car with smoke, low boost, or coolant/oil leaks.
Is the Kia Optima 2017-2020 a reliable used buy?
BYBA scores it 6.0/10 (buy with checks). 2 walk-away risks, 5 serious faults, 1 minor fault documented for this generation, weighted by severity and repair cost. Biggest factor: theta ii rod-bearing knock / engine seizure campaign exposure.
Get updates when this guide changes
Recalls get added, repair costs shift, and new fault patterns show up in the data. Leave an email and we'll tell you when the Kia Optima guide gets a meaningful revision. Nothing else, no selling your address.
Research basis
- nhtsa.gov: FWD
- kiaenginesettlement.com
- autosafety.org: hyundai-kia-fire-recall
- nhtsa.gov: recalls
- owners.kia.com: recalls.html
- apnews.com: hyundai-kia-recall-fire-risk-vehicles-park-outside
- nhtsa.gov: hyundai-kia-campaign-prevent-vehicle-theft
- ksupport.kiausa.com: SWLD
- iihs.org: hyundai-kia-theft-losses
- nhtsa.gov: FWD
- optimaforums.com
- nhtsa.gov: FWD
- RepairPal Kia Optima estimates
- NHTSA 2017 Optima Hybrid
- EPA Optima PHEV
- NHTSA 2017 Optima structure complaints
- RepairPal Kia Optima problems