Save P0301, associated codes and the operating conditions. If the light flashes or the engine shakes badly, reduce load and stop safely. Confirm the cause on the exact vehicle before buying a part; clear the code only after repair.
What P0301 means and when it becomes urgent
P0301 means a combustion misfire was detected on cylinder number 1. That number follows the manufacturer’s layout, so its physical location should not be guessed by looking at the engine from the front. P0300 describes random or multiple misfires; P0301 points to cylinder 1 without explaining why combustion is irregular.
Three illustrative situations help with the first decision. With a steady light and a slightly rough idle, save the information and arrange prompt diagnosis. If the light flashes, the car shakes or power drops sharply, avoid loading the engine and stop somewhere safe. If P0301 returns after a part has been replaced, do not continue buying parts at random: the original diagnosis is incomplete or another cause remains.
- Steady or flashing light, mild hesitation or severe shaking?
- P0301 alone, or P0300, P0302, injector or fuel-trim codes too?
- Cold start, hot idle, acceleration or after recent work?
- Fuel smell, smoke, mechanical noise, overheating or abnormal oil level?
A flashing check-engine light can accompany misfires that damage the catalytic converter. Controlling the vehicle takes priority over clearing the code.
Three official cases that rule out random parts replacement
The documents below do not establish a universal cause for P0301. They show that the decision depends on model, engine, model year, market, VIN and the tests already completed. The same code can require very different checks and repairs.
Honda first requires inspection of the affected spark plug and excludes its procedure when the plug is not fouled. Lexus requires diagnosis of the coil and a calibration check before its repair applies. The Jeep bulletin covers a PCM update for one exact diesel configuration and a broad set of possible symptoms or codes.
| Vehicle, energy and model year | Documented situation | Decision and limit |
|---|---|---|
| Honda Odyssey, petrol, all trims, 2013–2017 | P0301 to P0304 may occur with oil-fouled plugs under the stated condition. | Bulletin 25-061: inspect the plug and cylinders before the repair path. VIN eligibility required; US market. |
| Lexus RX 450h 2016–2019 and RX 450hL 2018–2019, 2GR-FXS petrol hybrid | P0301 to P0306 may occur; diagnosis must first identify a faulty ignition coil. | L-SB-0044-19 Rev1: check calibration, reprogram if required and replace the affected coil. US market. |
| 2021 Jeep Gladiator, 3.0 L V6 diesel with ESS, EXJ engine sales code | P0301 is one of several codes and symptoms covered by a PCM update. | 18-002-22 Rev. A: diagnosis and VIN check before reprogramming. North America and EMEA, exact configuration only. |
Evidence level: official manufacturer bulletins checked 17 October 2026. They are not OBDPhone® tests on these powertrains, failure-rate statistics or procedures to transfer to another vehicle.
Spark plug, coil, injector or mechanics: how to reason
A cylinder-specific misfire may come from ignition, injection, an air leak, wiring, compression or valve timing. Calibration and control strategy can also matter on certain engines. A wet, black or worn plug is evidence, but it may not identify what caused the fouling.
A technician can compare misfire counters, plug and coil condition, injector control, sealing and compression. Moving a coil to another cylinder can sometimes contribute to diagnosis, but it is neither universal nor risk-free: access, tightening procedures and high voltage vary. Do not unplug an injector or coil with the engine running to improvise a test.
Ask which observation separates each hypothesis and whether manufacturer information genuinely applies to your VIN. This avoids confusing the part affected by the problem — such as a fouled plug — with the underlying cause.
What to save before clearing the code
Capture P0301 with its status, every associated code and available freeze-frame data. Note mileage, engine temperature, rpm, load, when it occurred and recent work. Pending, current and stored codes do not tell exactly the same story.
After a real repair, scan again to see whether P0301 returns. Avoid clearing before the workshop visit because it removes clues and resets some monitors. There is no universal mileage that proves a repair is successful.
- Screenshot of P0301, its status and all associated codes.
- Freeze-frame rpm, temperature, load and speed when available.
- Precise symptoms and conditions: cold, hot, rain, acceleration or idle.
- Recent repairs, oil level and date of the last ignition service.
How OBDPhone® helps
OBDPhone® reads generic engine and emissions fault codes and available engine data. It helps save P0301, P0300 and associated codes, plus context for the repairer. The values actually available depend on the vehicle.
OBDPhone® does not measure compression or confirm the condition of a plug, coil or injector. ABS, airbags, traction batteries, coding, programming and manufacturer-specific functions are not guaranteed. Clear only after repair. Check your vehicle or contact support@obdphone.com. Official sources last checked 17 October 2026.
Understand injector-circuit code P0201 →
Frequently asked questions
The essential answers.
Does P0301 mean the cylinder 1 coil has failed?+
No. The coil is one possibility. Honda, Lexus and Jeep bulletins show that the vehicle-specific cause and decision may be mechanical, electrical or software-related.
Can I drive with P0301?+
With a flashing light, severe shaking or power loss, reduce load and stop safely. With a steady light, avoid unnecessary journeys and arrange prompt diagnosis.
What is the difference between P0300 and P0301?+
P0300 covers random or multiple misfires; P0301 means the controller assigns misfires to cylinder 1. Neither gives the cause by itself.
Should I clear P0301 before visiting a workshop?+
No. Save the code, status, associated faults and freeze-frame data. Clear it only after repair.
This guide supports an initial understanding. It does not replace the vehicle manual, manufacturer safety instructions or an assessment by a qualified professional.
Primary sources
Reviewed to verify the facts and show why procedures depend on the vehicle.