P0301 Code-Cylinder 1 Misfire-Causes and Fixes

By Carista Team

P0301 Code-Cylinder 1 Misfire-Causes and Fixes

 

Key Takeaways

  • P0301 Code Meaning: Indicates a misfire in cylinder 1.
  • Common Causes: Faulty spark plugs, ignition coils, fuel injectors, or compression issues.
  • Symptoms: Rough idling, engine shaking, reduced fuel efficiency, and check engine light.
  • Best Fix Approach: Diagnose with a reliable OBD2 scanner like Carista, inspect ignition/fuel systems, and repair accordingly.
  • Prevention: Regular maintenance and early diagnosis reduce costly repairs.

 

What is the P0301 Code?

The P0301 code is an engine trouble code that tells you cylinder 1 in your engine is misfiring. A misfire happens when the fuel and air mixture in a cylinder doesn’t burn the way it should. This can be caused by problems with the spark (ignition), fuel delivery, or even engine mechanics.

When a misfire occurs, the engine may run rough, lose power, or use more fuel than normal. That’s why the check engine light comes on — your car’s computer has detected that cylinder 1 isn’t working properly and is warning you before the issue gets worse.

In short: P0301 means your engine isn’t firing correctly in its first cylinder, and it needs attention to avoid further damage.

This can cause rough performance, reduced power, and increased emissions. If ignored, it can damage your catalytic converter and lead to expensive repairs.

 

Common Symptoms of P0301 Code

You’ll likely notice one or more of these issues:

  • Rough idling or shaking engine
  • Check Engine Light illuminated
  • Reduced fuel economy
  • Loss of acceleration/power
  • Difficulty starting the vehicle
  • Strong fuel odor from exhaust

Close-up of a car speedometer with the yellow check engine light illuminated, indicating a possible engine issue such as a cylinder misfire or diagnostic trouble code.

 

P0301 Code Meaning

  • P → Powertrain

    • The problem is related to the engine or transmission system.

  • 0 → Generic Code

    • It’s an SAE-standard OBD-II error code, valid for all makes and models.

  • 3 → Ignition System / Misfire

    • Points to the ignition system, specifically misfire detection.

  • 01 → Cylinder 1 Misfire

    • The last two digits identify the affected cylinder. “01” means a misfire in cylinder 1.

Therefore, P0301 = Cylinder 1 Misfire Detected.

Common Causes of P0301 Cylinder 1 Misfire

A Cylinder 1 misfire can stem from various ignition, fuel, mechanical, and sensor-related problems. Here’s a full breakdown:

1. Ignition System Issues

  • Worn Spark Plug: Carbon buildup, worn electrode, or incorrect gap.
  • Faulty Ignition Coil/Coil Pack: Weak or no spark delivery.
  • Bad Spark Plug Wire/Boot: Electrical arcing, cracks, or moisture damage.

2. Fuel System Problems

  • Clogged or Dirty Fuel Injector: Inadequate fuel spray pattern.
  • Leaking Injector: Too much fuel causes misfires or flooding.
  • Low Fuel Pressure: Faulty fuel pump, clogged filter, or weak pressure regulator.
  • Poor Fuel Quality: Contaminated or watered-down gas causing improper combustion.

3. Air and Vacuum Leaks

  • Vacuum Leak Near Cylinder 1: Extra air disrupts the air-fuel ratio.
  • Leaking Intake Manifold Gasket: Especially around cylinder 1 runner.
  • Throttle Body Carbon Buildup: Restricts airflow and causes misfires at idle.

4. Engine Mechanical Problems

  • Low Cylinder Compression: From worn piston rings, valve leaks, or head gasket failure.
  • Burnt or Bent Valves: Prevents proper sealing.
  • Worn Camshaft Lobe: Affects valve timing for that cylinder.
  • Timing Chain/Belt Issues: Incorrect valve timing leads to misfires.

5. Sensor & Electronics Faults

  • Bad Crankshaft Position Sensor: Incorrect ignition timing signals.
  • Faulty Camshaft Position Sensor: Causes incorrect valve timing reference.
  • Oxygen (O2) Sensor Problems: Poor feedback loop can mismanage fuel delivery.
  • Mass Air Flow (MAF) Sensor Issues: Incorrect air intake readings create lean or rich conditions.
  • Engine Control Unit (ECU/PCM) Glitch: Rare but possible misfire mismanagement.

6. Exhaust & Emissions-Related

  • Exhaust Gas Recirculation (EGR) Malfunction: Stuck EGR valve introduces exhaust gases at the wrong time.
  • Clogged Catalytic Converter: Causes backpressure, disrupting cylinder combustion.

 

How to Diagnose P0301 Code?

The best way to confirm a cylinder misfire is with a professional-grade OBD2 scanner.

Step 1: Use an OBD2 scanner (like Carista) to read the fault codes.

Step 2: Inspect the spark plugs, coils, and injector for cylinder 1.

Step 3: Perform a compression test if ignition/fuel parts are fine.

Step 4: Rule out vacuum leaks and sensor failures.

 

How to Fix P0301 Code?

Depending on the cause, common fixes include:

  • Replacing spark plugs or ignition coils
  • Cleaning or replacing the fuel injector
  • Repairing vacuum leaks
  • Fixing wiring/connection issues
  • Conducting engine repairs if low compression is found
 

Expert advice: Always clear the code after repairs and test drive your car to ensure the issue is resolved.

 

Why Use the Carista OBD2 Scanner & App?

The Carista OBD2 scanner and mobile app make diagnosing codes like P0301 easy and accurate. But it has many other features: 

  • Instant Check Engine Diagnostics – Reads codes with detailed explanations.
  • Customization Features – Adjust hidden car settings (lights, locks, etc.).
  • Live Data Monitoring – Track performance metrics in real time.
  • User-Friendly App – Works seamlessly on iOS and Android.

Instead of guessing, Carista helps you pinpoint the exact issue, saving you time and costly mechanic visits.

Image showing Carista app ratings: 4.6 stars on the Apple App Store, 4.5 stars on Google Play Store, and 4.4 stars on Amazon.

 

FAQs About P0301 Code

Q1: Is it safe to drive with a P0301 code?

Not recommended. Driving with a misfire can damage your catalytic converter and worsen engine problems.

Q2: Can bad gas cause a P0301 code?

Yes, contaminated or poor-quality fuel can cause temporary misfires.

Q3: How much does it cost to fix P0301?
  • Spark plugs: $50–150
  • Ignition coil: $100–300
  • Fuel injector: $150–400
  • Engine repair (if compression issue): $1,000+
Q4: Will replacing spark plugs fix P0301?

Often, yes—especially if they are old or worn out. However, you must confirm the root cause with an OBD2 scanner.

Q5: How can I prevent cylinder misfires?

Routine maintenance—changing spark plugs, keeping fuel clean, and timely inspections—prevents most misfires.

 

Final Thoughts

The P0301 Cylinder 1 Misfire code signals a potentially serious issue that requires prompt attention. By diagnosing with a trusted tool like the Carista OBD2 scanner and app, you can save time, prevent further engine damage, and restore your vehicle’s performance.

Disclaimer: This article is for informational purposes only and is not a substitute for professional mechanical advice. Always consult a qualified mechanic for serious automotive issues.