P0301 localizes misfire to Elantra cylinder 1 but does not identify the coil. Confirm cylinder numbering from the exact engine manual, preserve cold/load counts, inspect the labeled plug and make one controlled ignition comparison. If the fault stays, test injector delivery and compression/leak-down. Hyundai's 2017 AD/ADA 2.0L bulletin and selected 2022 Elantra N injector bulletin have strict applicability; neither authorizes the same repair on every Elantra P0301.
Match the symptom
Select the closest observation. The result changes the first test; it does not name a part to replace.
Stop loading.
What can set P0301—and how to separate it
The order below is evidence-driven, not a universal probability ranking. Vehicle year, repair history, companion codes and the operating condition in freeze frame change where diagnosis should begin.
| Possible cause | Evidence that supports it | First useful test |
|---|---|---|
| Cylinder 1 plug fouled/worn/cracked | Abnormal deposit/gap | Labelled plug |
| Ignition component/circuit | Controlled test follows | Targeted ignition test |
| Injector fault | Count stays/contribution differs | Balance/command |
| Compression/valvetrain | Low mechanical contribution | Compression/leak-down |
| Cam/crank timing fault | P0016/P0340/sync data | Correlation diagnosis |
Use one controlled ignition test
Keep plug 1 labeled and compare gap, deposits, cracking and fuel wetness with a neighboring cylinder. Move one known-good coil only when the hardware permits and monitor whether the count follows.
If P0301 stays on cylinder 1, return the known-good component. Further swapping destroys evidence and does not test fuel or compression.
Test injector and sealing when ignition passes
Use GDS contribution and engine-specific pressure/balance methods. Direct-injection fuel components retain dangerous pressure and require factory procedures.
Measure compression and leak-down under comparable temperature. Valve sealing, cylinder damage or cam timing can keep the count on one hole.
Apply Hyundai bulletins only at their boundaries
The 2017 bulletin combines ECM logic and coil inspection for its exact AD/ADA 2.0L branch. The 2022 N bulletin concerns selected injectors by production data.
Verify no cylinder 1 counts under the original safe condition and no pending P0301. A software update cannot restore compression or seal an injector.
Save these scan-data clues
Freeze frame is a snapshot of conditions when the PCM matured the fault. It can distinguish an idle-only problem from a load, cold-start or monitor-completion problem. Clearing first throws that context away.
- Exact VIN, platform, model year and engine sales code
- All confirmed, pending and permanent companion codes
- RPM, load, coolant temperature and vehicle speed
- Relevant commanded and actual scan data
- Recent service, repairs and symptom conditions
- Manufacturer bulletin and current software/VIN status
A practical diagnostic workflow
- 01Identify engine and cylinder 1
Use exact diagram.
- 02Preserve condition
Capture cold/load counters.
- 03Inspect plug
Keep labeled.
- 04Test ignition once
Watch whether count moves.
- 05Test injector and sealing
If it stays.
- 06Check timing companions
Do not ignore correlation.
- 07Retest
Verify original conditions.
Do not replace the most commonly named component from P0301 alone. Confirm the exact engine, preserve evidence and complete the manufacturer test sequence before ordering parts.
Why the model year changes the test
Elantra diagnostics span multiple sedan, Coupe, GT, Sport, N Line, Hybrid and Elantra N generations with Beta, Gamma, Nu, Kappa, Smartstream and Theta-family engines. MPI, GDI, turbocharging, CVVT, intake-runner hardware, EVAP design and campaign coverage differ sharply. Confirm VIN, body style, model year, engine code, production date, market and ECM ROM before applying any bulletin, definition or component diagram.
- 20-FL-001H covers certain 2017 AD/ADA 2.0L vehicles.
- 24-FL-006H covers a production-bounded group of 2022 Elantra N vehicles.
- MPI and GDI injector tests require different equipment and safety.
- P0017 or P0014 companions raise timing priority.
P0301 FAQ
Is P0301 always a coil?+
No.
Can I drive?+
Not with flashing MIL or shaking.
Can I swap coils?+
Yes when engine hardware supports it.
What if it stays?+
Test injector and compression.
Can valves cause it?+
Yes.
Why check timing codes?+
They may explain the misfire.
Should I clear first?+
No.
What confirms repair?+
No cylinder 1 counts under original conditions.
Ford diagnostic references
These documents explain Ford monitor operation. Exact pinpoint tests, connector views and specifications must be selected for the truck's VIN and model year in current service information.
01Hyundai TSB 20-FL-001H — 2017 Elantra 2.0L misfireNarrow 2017 AD/ADA 2.0L ECM update and ignition-coil inspection path for P0300–P0304↗02Hyundai TSB 24-FL-006H — selected 2022 Elantra N injectorsLimited production-date/VIN-origin 2022 Elantra N 2.0T branch for P0300–P0304 caused by injector internal filter breakage↗03Hyundai TechInfoOfficial VIN-, engine- and model-year-specific shop-manual and GDS procedures↗04Hyundai manuals and warranty informationOfficial model-year owner manuals, warnings and maintenance information↗