P0300 means multiple Santa Fe cylinders misfired or no one cylinder dominated. Preserve P0301–P0306 counts, bank trims, rail pressure, temperature and load. Hyundai TSB 25-FL-001H covers only production-bounded 2021–2022 TMA Santa Fe non-turbo 2.5L GDI vehicles for internally leaking injectors and an all-four replacement kit. Older V6, Theta 2.4L/2.0T, hybrid and other Smartstream engines need their own ignition, injector, air/fuel, compression and timing tests.
Match the symptom
Select the closest observation. The result changes the first test; it does not name a part to replace.
Stop loading to protect catalysts.
What can set P0300—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 |
|---|---|---|
| Worn/fouled plug or ignition fault | Cylinder leader and controlled swap follows | Labelled plug/ignition test |
| Injector or fuel-pressure fault | Contribution/pressure mismatch | Injector/fuel tests |
| Intake, purge or boost leak | Trim/smoke pattern | Smoke and purge test |
| Compression, valvetrain or timing fault | Count stays with mechanical weakness | Compression/leak-down/timing |
| Shared voltage or contaminated fuel | All cylinders or post-refueling | Voltage/fuel-quality test |
Preserve the cylinder and bank pattern
Capture counts at cold start, idle and the freeze-frame load. Label plugs and make one controlled ignition comparison instead of moving a whole set.
A V6 one-bank pattern favors local intake, fuel or cam causes; all cylinders raise shared airflow, pressure, voltage or contaminated fuel.
Use the 2.5L injector bulletin only at its boundary
The 2025 bulletin names selected 2021–2022 Santa Fe TMA 2.5L non-turbo production. Verify date, VIN origin and history before applying its all-four-injector instruction.
A different year, turbo, V6 or hybrid does not inherit that repair. Test injector contribution and low/high pressure under its own shop manual.
Prove mechanical health when the count stays
If misfire does not follow a valid ignition test, measure injector contribution, compression and leak-down. P0014/P0017 companions raise timing priority.
Verify stable counts under the original safe condition and no pending P0300. Catalyst evaluation comes after combustion is controlled.
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 bank layout
Cylinder patterns differ.
- 02Preserve counters
Save cold/load evidence.
- 03Inspect plugs in order
Deposits direct testing.
- 04Target ignition
Use one controlled test.
- 05Test fuel and air
Graph pressure/trims and smoke paths.
- 06Prove mechanical health
Use compression/leak-down/timing.
- 07Verify original condition
Avoid a flashing-MIL road test.
Do not replace the most commonly named component from P0300 alone. Confirm the exact engine, preserve evidence and complete the manufacturer test sequence before ordering parts.
Why the model year changes the test
Santa Fe diagnostics span CM, Santa Fe Sport DM/AN, XL three-row and newer TM/MX5 generations with inline-four, turbo, V6, hybrid and plug-in powertrains. MPI, GDI, CVVT, intake-runner hardware, catalyst banks, EVAP routing and P1326 campaign coverage differ. Confirm VIN, model year, Santa Fe versus Santa Fe Sport/XL, engine code, drivetrain, production date and ECM ROM before applying a bulletin or diagram.
- 25-FL-001H is limited by engine, production dates and VIN origin.
- Inline-four and V6 cylinder/bank patterns require different interpretation.
- GDI rail work requires high-pressure safety and one-time-use parts.
- A flashing MIL means reduce load immediately to protect catalysts.
P0300 FAQ
Does P0300 mean all coils failed?+
No.
Can I drive?+
Not with flashing MIL or strong shaking.
Can bad fuel cause it?+
Yes.
Should I replace plugs first?+
Inspect and record them first.
Can vacuum leaks cause it?+
Yes.
Can timing cause it?+
Yes, especially with cam/crank codes.
Why save counters?+
They reveal cylinder and bank structure.
What confirms repair?+
Stable counters 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 25-FL-001H — selected Santa Fe 2.5L GDI misfireProduction-bounded 2021–2022 Santa Fe TMA non-turbo 2.5L branch for P0300–P0304 and all-four GDI injector replacement↗02Hyundai TechInfoOfficial VIN-, engine- and model-year-specific shop-manual and GDS procedures↗03Hyundai manuals and warranty informationOfficial model-year owner manuals, warnings and maintenance information↗