When your air-fuel mixture doesn’t burn properly, your engine starts misfiring. A misfire can be easily noticed by retrieving the activation code from the car’s onboard diagnostics system. The P0301 code is one of a series of OBD-II trouble codes that are triggered when your powertrain control module (PCM) has detected a misfire. This article mainly explains the P0301 code meaning, symptoms, and causes.
P0301 Code Definition
The trouble code P0301 stands for “Cylinder 1 Misfire Detected.”
What does the P0301 Code mean?
The P0301 code indicates that your powertrain control module (PCM) has detected that cylinder number 1 is misfiring.
When your engine misfires, your PCM triggers the check engine light and may put the car into limp mode to avoid further damage. The check engine light will remain until the code is repaired.
The vehicles usually contain 4, 6, or 8 cylinders. These cylinders are arranged in different arrangements. The engine cylinder has different parts including the spark plug, fuel injector, ignition coil, and piston ring.
As you increase the number of cylinders, your engine power will be increased. A piston moves upward and downward inside the cylinder at a specific time. Misfires generally occur when this ignition timing is off.
When the air-fuel mixture is burned inside the cylinder, it generates power. This power is used to rotate the crankshaft of your engine. The rotation of the crankshaft is further used to turn the flywheel which further turns the vehicle wheels.
The crankshaft rpm of your engine can decrease or increase when the engine cylinder starts misfiring. When the PCM detects that there is an increase or decrease of the crankshaft revolutions per minute that is more than 2%, it stores a trouble code.
As the PCM/ECM detects that your engine cylinder number 1 is misfiring, it triggers the trouble code P0301.
Symptoms of P0301 Code
A vehicle with a P0301 code may produce one or more of the following symptoms:
- Engine stalling
- Fuel smell from the exhaust pipe
- Hard to start the vehicle or won’t start at all
- Poor fuel efficiency
- Vehicle idles rough
- Check engine light illumination
- Limp mode
- Misfires
- A reduction in the engine power
- Poor acceleration
- Jerking and vibration during driving
Causes of the P0301 Code
The P0301 engine code is triggered due to one or more of the following causes:
- Faulty EGR valves
- Poor compression in cylinder 1
- Bad or damaged fuel injectors
- An issue with the engine valves
- Bad fuel pump
- Inaccurate ignition timing
- Bad camshaft sensor
- Bad spark plug in cylinder 1
- Poor quality fuel
- Insufficient fuel
- Damaged wiring of the cylinder 1 spark plug
- Bad catalytic converter
- Damaged distributor cap
- Head gasket leak
- Faulty MAF sensor
- Faulty fuel pressure sensor
- Faulty crankshaft sensor
- Bad Oxygen sensor
- Oil distributor failure
- A damaged lifter or worn camshaft lobe
- A faulty throttle position sensor
- Vacuum leaks
- Low fuel pressure
- Bad ignition coils in cylinder 1
- Bad PCM
How to Diagnose the P0301 Code?
You need the following tools to diagnose or fix the P0301 code:
- Plug spanner
- Screwdrivers
- Digital Multimeter
- Leakdown tester
- Compression tester
- Pliers
- Spark plug wires
- Fuel pressure gauge
- OBD-II scan tool
- Spark plugs
- Socket, ratchet, and extension
Follow the below-given steps to diagnose the P0301 code:
- Use an OBD-II scan tool to check the existence of the P0301. Collect all trouble codes and freeze frame data stored by the PCM.
- Clear the codes and test drive the car to check if the P0301 trouble code returns
- Inspect the loose engine ground wiring.
- Check for loose connectors at the ignition coils.
- Inspect the wiring for damage (especially cylinder 1).
- Inspect the coil pack wires for damage or excessive wear
- Check the spark plug of cylinder 1. A bad spark plug is one of the major causes of the misfire. If the spark plug is bad, replace it.
- Inspect and replace the coil pack wiring, coil packs, or spark plug wiring if needed.
- After all the above-given repairs and inspection, make a test drive. If the P0301 code returns, then inspect the fuel injector and fuel injector wiring for cylinder 1.
- If your vehicle has a distributor cap and rotor button, then inspect them for excessive wear, cracks, corrosion, or any other damage.
- Inspect the cylinder 1 compression system.
- Diagnose and fix any other trouble codes that have been stored by the PCM and are associated with the P0301 code.
- Repeat a test drive to see if the P0301 code returns.
- If your vehicle again triggers this trouble code, an issue with the PCM is possible. Update the PCM software or replace it if needed.
Common P0301 Code Diagnosis Mistakes
- It is necessary to visually inspect the fuel injector wiring for damage before replacing the coil pack wires, coil packs, spark plug wires, and spark plugs.
- Not properly inspecting all the parts
- Not diagnosing and necessary repairs of other associated trouble codes stored by the PCM
- Clearing the code without first confirming the main issue
- Replacing the unnecessary components
What repairs can fix the P0301 Code?
One or more of the following repairs can fix the P0301 code:
- Replacing the bad spark plug
- Replacing the blown head gasket
- Replacing the bad fuel pump
- Repairing the damaged engine cylinder
- Repairing the fuel rail leak
- Replacing the bad catalytic converter
- Replacing the bad MAF sensor
- Replacing the damaged or corroded spark plug wires
- Replacing the bad crankshaft position sensor
- Replacing the burned valves
- Replacing the bad or damaged fuel injectors
- Replacing the bad camshaft position sensor
- Replacing the bad rotor button and distributor cap
- Replacing or repairing the damaged coil pack wires
- Replacing the bad O2 sensor
- Replacing the bad throttle position sensor
- Replacing the bad EGR valve
- Repairing the vacuum leak
- Diagnosing and repairing any related trouble codes stored by the PCM
Repair Costs for P0301 Code
After diagnosing, the P0301 code may need one or more of the following repairs to fix the original problem.
| Parts | Cost |
| Ignition Coil replacement | $220 to $650 |
| Fuel pump replacement | $250 to $1,090 |
| Fuel injector replacement | $1400 to $2000 |
| Spark plug wiring repair | $170 to $250 |
| Spark Plug replacement | $60 to $260 |
How To Prevent P0301 Code?
To prevent the P0301 engine code from triggering, you need to follow the following control measures:
- Ensure the use of good quality fuel because bad quality fuel may have impurities that may clog or damage different parts and cause engine misfire.
- Regular maintenance of the ignition system components, including the ignition coils and spark plugs.
- Cleaning or replacement of the fuel injectors according to the manufacturer’s recommended intervals
- Regular maintenance of the air intake and filters
- The use of good-quality oil
- Regular maintenance of the exhaust system
- Avoid harsh driving
- The regular cleaning of the EGR system’s components according to the manufacturer’s recommendations
- Ensure regular inspection of the vacuum system for a leak
- Regular inspection of your vehicle by a mechanic to find any possible problems early on.
FAQ Section
How serious is the P0301 code?
The P0301 code is considered a serious trouble code. This code generates different drivability issues, such as engine stalling, poor fuel economy, or low engine power. Driving with this code may become hazardous if your vehicle randomly stalls or stops while the vehicle is being operated. Therefore, you should address the P0301 trouble code as soon as possible.
How do I fix a misfire?
- Adding more fuel if the fuel level is less than a specific level
- Replacing the bad O2 sensor
- Replacing the bad fuel pump
- Replacing the bad spark plug
- Replacing the bad fuel injector
- Replacing the bad fuel filter
- Replacing the bad fuel pressure sensor
What causes cylinder 1 to misfire?
- Faulty EGR valves
- Poor compression in cylinder 1
- Bad or damaged fuel injectors
- Burned or bad engine valves
- Bad fuel pump
- Inaccurate ignition timing
- Bad camshaft sensor
- Bad spark plug in cylinder 1
- Poor quality fuel
- Insufficient fuel
- Damaged wiring of the cylinder 1 spark plug
- Bad catalytic converter
- Damaged distributor cap
- Head gasket leak
- Faulty MAF sensor
- Faulty fuel pressure sensor
- Faulty crankshaft sensor
- Bad Oxygen sensor
- Oil distributor failure
- A damaged lifter or worn camshaft lobe
- A faulty throttle position sensor
- Vacuum leak
- Low fuel pressure
- Bad ignition coils in cylinder 1
Can you drive with a P0301?
You should not drive with a code P0301. This code indicates the engine is misfiring. The misfire is very dangerous for your vehicle engine. The misfire may badly damage your engine. Therefore, you shouldn’t drive your vehicle with this code. This code must be addressed as soon as possible.
How serious is a cylinder 1 misfire?
A cylinder misfire in your vehicle is a serious problem that could lead to significant damage to your engine. If you suspect you have a misfiring cylinder, it’s important to get it inspected and taken care of quickly.
What are the causes of a misfire?
The following are the major causes of a misfire:
- Bad throttle position sensor
- Faulty EGR valves
- Bad ignition coils
- Low fuel pressure
- Bad compression system
- Oil distributor failure
- Bad or damaged fuel injectors
- Vacuum leaks
- Burned or bad engine valves
- Bad fuel pump
- A damaged lifter or worn camshaft lobe
- Inaccurate ignition timing
- Bad camshaft sensor
- Bad spark plugs
- Bad Oxygen sensor
- Poor quality fuel
- Insufficient fuel
- Faulty crankshaft sensor
- Damaged wires or connectors
- Bad catalytic converter
- Faulty fuel pressure sensor
- Damaged distributor cap
- Head gasket leak
- Faulty MAF sensor
- Bad PCM