P0302 Code: Meaning, Symptoms, Causes (& How to Fix it)

The proper combustion of the air-fuel mixture is very important for the efficient working of the engine. 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 P0302 code also indicates the misfire in an engine cylinder.

P0302 engine Code

These trouble codes represent particular conditions and are generally related to the affected cylinder(s). The diagnostic trouble code (DTC) P0302 represents a misfiring in engine cylinder 2. This article mainly explains the P0302 code symptoms, causes, and fixing costs.

P0302 Code Definition

The P0302 code stands for “Cylinder 2 misfire detected.”

What Does the P0302 Code Mean?

The P0302 code indicates that your powertrain control module (PCM) has detected that engine cylinder number 2 is misfiring.

P0302 Code

The vehicles most commonly contain four or six cylinders. These cylinders are arranged in different arrangements. The engine cylinder is also known as a combustion chamber. After the compression process, the air-fuel mixture is transferred into the engine cylinder.

Each cylinder contains a spark plug. The spark plugs are only used in gasoline engines. In the case of the gasoline engine, when the compressed air-fuel mixture enters the cylinder, the spark plug generates an electric spark and ignites the air-fuel mixture. However, in the case of a diesel engine, the air-fuel mixture is ignited due to the high compression of the air.

As the combustion of the air and fuel mixture starts, it produces power. This output power is utilized to turn the crankshaft. As the crankshaft rotates, it turns the flywheel which further rotates the wheels of your car.

Your vehicle’s crankshaft revolutions may decrease or increase if a cylinder misfires. If the rpm/min increases or decreases by more than 2%, your PCM triggers a trouble code.

The check engine light of your vehicle will start to illuminate if there is a 2% to 10% change in the rotation speed of the crankshaft. Similarly, if the crankshaft’s RPM increases or decreases by 10 percent, the check engine light will start flashing, indicating a more serious issue, typically related to misfiring.

When you see a flashing Check Engine Light, it suggests a serious issue with misfiring. When your powertrain control module (PCM) detects that your engine cylinder number 2 is misfiring, it triggers the P0302 code.

The P0302 code is part of a series of misfire trouble codes that range from P0300 to P0012. Each code between P0301 and P0312 specifies a misfire on a specific cylinder. For example, code P0301 indicates a misfire on cylinder number 1, and code P0312 indicates a misfire on cylinder number 12.

Causes of P0302 Code

The P0302 engine code is a serious trouble code. It indicates engine misfiring. Your vehicle’s computer triggers the P0302 engine code due to one or more of the following causes:  

  • Faulty EGR Valves
  • Faulty Fuel Injectors
  • Burned or bad engine valves
  • Bad Fuel Pump
  • Bad Spark Plug
  • Low Fuel Levels
  • Damaged Wires
  • Blow Head Gasket
  • Faulty MAF Sensor
  • Faulty Fuel Pressure Sensor
  • Faulty O2 Sensor
  • Faulty Throttle Position Sensor
  • Vacuum Leaks
  • Faulty Crankshaft Sensor
  • Poor Quality Fuel
  • Bad Camshaft Sensor
  • Bad Ignition Coils
  • Low Compression
  • Bad Catalytic Converter
  • Bad Timing Belt/Chain

Let’s discuss these causes of P0302 trouble code in detail:

1) Faulty EGR Valves

The EGR valve is considered one of the most common causes of the P0302 code. The main function of the EGR valve is to control the exhaust emissions.

However, an issue with the EGR valve may disturb the air-fuel mixture in engine cylinder 2 and cause the engine cylinder to misfire. 

2) Faulty Fuel Injectors

The fuel injector plays a vital role in ensuring the proper combustion of the air-fuel mixture within the combustion chamber. It ensures the proper injection of fuel into the combustion chamber.

When something goes bad with the fuel injector, it may disrupt the air-fuel ratio and lead to engine misfires.

3) Bad Engine Valves

For the proper combustion of the air-fuel mixture, it is important that intake and exhaust valves open and close at the right time.

If any of these valves don’t open at the right time, it may disturb the air and fuel mixture. When the air and fuel mixture is disturbed, it may lead engine cylinder 2 to misfire.

4) Bad Fuel Pump

The fuel pump is used to deliver the fuel from the fuel tank to the fuel injection system. Whenever something goes bad with the fuel pump, it may stop the proper supply of fuel to the fuel injection system and disturb the air-fuel mixture.

5) Bad Spark Plug

The main purpose of the spark plug is to ignite the air-fuel mixture at the right time. When it goes bad, it doesn’t ignite the air-fuel mixture properly and causes misfiring. 

6) Low Fuel Levels

Your engine requires a sufficient supply of fuel to perform efficiently. The low fuel level can lead to a poor air-fuel mixture and cause misfiring. 

7) Damaged Wires

The damaged wires or loose connections related to cylinder 2 may affect the functionality of the fuel injection system or ignition system and lead to misfires.

8) Blow Head Gasket

The main function of the head gasket is to seal the combustion chamber and ensure proper compression while the engine is operating. A blown head gasket may lead combustion gases to leak into adjacent cylinders and cause misfiring. 

9) Faulty MAF Sensor

The MAF sensor is used to measure the mass flow rate of air entering the engine cylinder. When the MAF sensor goes bad, it doesn’t properly measure the air volume readings, disturbing the fuel-air mixture and leading to engine misfiring.

10) Faulty Fuel Pressure Sensor

The fuel pressure sensor measures the fuel pressure within the fuel rails. The PCM of your vehicle uses the data of the fuel pressure sensor to adjust the air-fuel ratio.

When this sensor goes bad, it starts sending wrong information to the PCM and disturbs the air-fuel ratio. In this way, it may cause misfires. 

11) Faulty O2 Sensor

An issue with the oxygen sensor may badly affect the air and fuel mixture, causing misfiring. 

12) Faulty Throttle Position Sensor

The throttle position sensor is used to measure the position of the throttle valve. The PCM uses this data to adjust different aspects such as fuel injection rate, ignition timing, and many more.

When this sensor becomes faulty, it may send the wrong data to the PCM and disturb the fuel injection rate and ignition timing. 

13) Vacuum Leaks

The proper performance of the vacuum system is very important to maintain the proper air-fuel ratio. When the vacuum system leaks, unwanted air entering the intake manifold may affect the air-fuel mixture, potentially leading to misfires.

14) Faulty Crankshaft Sensor

The crankshaft sensor measures the speed and position of the crankshaft and sends this data to the PCM. The PCM utilizes this data to adjust the fuel injection rate and ignition timing.

An issue with the crankshaft position sensor may disturb the proper combustion of the air-fuel mixture and cause misfires. 

15) Poor Quality Fuel

The low-quality fuel usually contains different impurities that may clog different parts of your engine like the fuel injector. Therefore, low-quality fuel may affect the air-fuel ratio, causing misfires. 

16) Bad Camshaft Sensor

The camshaft sensor measures the performance of the camshaft. The vehicle’s computer uses the data of this sensor to regulate different functions including the fuel injection rate.

When this sensor goes bad, it may affect the air-fuel mixture and lead to poor combustion of the air-fuel mixture. 

17) Bad Ignition Coils

The ignition coils help the spark plugs to produce strong spark according to the requirements. When the ignition coil becomes faulty, it leads to a lack of spark and causes misfires. 

18) Low Compression

The compression pressure within the engine cylinder must be sufficient to ensure proper combustion of the air-fuel mixture. If the compression in your engine cylinder 2 is low, it causes misfiring and a P0302 code.

19) Damaged Timing Belt

The timing belt of your car plays an important role to ensure the proper synchronization of the engine’s components. It ensures the proper rotation of the camshaft and crankshaft. When this belt is damaged or worn, it may disturb the rotation of the camshaft and crankshaft, causing misfiring.  

Symptoms of P0302 Code

Driving a vehicle with P0302 code produces one or more of the following symptoms:

  • Engine stalling
  • Fuel smell from the exhaust pipe
  • The vehicle will not start or is difficult to start
  • Poor fuel economy
  • Rough idle
  • Illuminated check engine light
  • Limp mode
  • Misfires
  • A reduction in the engine power
  • Poor car acceleration
  • Jerking when driving

Read More: P0303 Code Symptoms and Causes

How to diagnose the P0302 Code?

Follow the following basic steps to properly diagnose the P0302 code. However, it is recommended to consult with your vehicle’s service manual to find the diagnostic steps for your specific model.

  • Use an OBD-II scan tool to check the existence of the P0302.
  • Record all stored fault codes, along with all available freeze frame data. Clear the codes and make a test drive. If the code returns, then check other parts.
  • Inspects the spark plug wire for cylinder 2 for corrosion or damage.
  • Inspect the loose engine ground wires.
  • Check for loose connectors at the ignition coils.
  • Check the spark plug of cylinder 2. A bad spark plug is one of the major causes of the misfire. If the spark plug is bad, replace it.
  • Inspect the coil pack wires for damage or corrosion.
  • 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 P0302 code returns, then inspect the fuel injector and fuel injector wiring for cylinder 2.
  • 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 2 compression system.
  • If your vehicle again triggers the P0302 code, an issue with the PCM is possible. Update the PCM software or replace it if needed.

Common P0302 Code Diagnostic Mistakes

  • Not properly inspecting all the parts
  • Replacing the unnecessary components
  • Inability to confirm the presence of the P0302 code
  • Clearing the code without first verifying the problem
  • Not clearing the PCM codes after fixing the codes
  • Replacing the spark plug or fuel injector without inspecting the wiring and connectors

Repair Costs for P0302 Code

The repair or fixing cost of the P0302 code varies according to labor cost, the vehicle model, and your area. To fix this code, you may need one or more of the following repairs:

Spark plug replacement$60 to $260
Spark plug wiring repair$170 to $250
Fuel injector replacement$1400 to $2000
Ignition coil replacement$220 to $650
Fuel pump replacement$250 to $1,090

What repairs can fix the P0302 code?

One or more of the following repairs can fix the P0302 engine code:

  • Replacing the bad spark plug
  • If your cylinder is damaged, then replace it.
  • Replacing the damaged or corroded spark plug wires
  • Replacing the bad or damaged fuel injectors
  • Replacing the faulty ignition coils
  • Replacing the faulty throttle position sensor
  • Replacing the bad EGR valve
  • Replacing the bad O2 sensor
  • Replacing the burned valves
  • Replacing the bad MAF sensor
  • Repairing the fuel rail leaks
  • Repairing the vacuum leaks
  • Replacing or fixing the head gasket leaks
  • Replacing the bad crankshaft position sensor
  • Replacing the bad camshaft position sensor
  • Replacing the bad rotor button and distributor cap
  • Replacing the bad catalytic converter
  • Replacing the bad internal engine parts
  • Diagnosing and repairing any related trouble codes stored by the PCM
  • Replacing the bad fuel pump

How serious is the P0302 code?

The P0302 trouble code is considered a serious trouble code. It makes your vehicle hard to drive. This code indicates a misfire. It produces different drivability issues, such as stalling, poor acceleration, or poor fuel economy. You should fix the misfiring promptly. Driving with P0302 for a long time may lead to the complete failure of your engine.

FAQ Section

How much does it cost to fix a cylinder 2 misfire?

It is very hazardous to drive a vehicle with a bad cylinder or misfiring cylinder. If your cylinder is misfiring, then fix it as soon as possible to prevent yourself from an expensive repair. The average repair cost to fix a cylinder 2 misfire is from $90 to $1100, depending on the reason for the misfire.

Can low fuel cause a P0302 code?

Yes, insufficient fuel or low fuel pressure is one of the major causes of the P0302 code. When your engine has low fuel, there will be no proper supply of fuel to the engine cylinder, which will cause a misfire.

Can a bad Oxygen sensor cause misfire in the cylinder?

If your O2 sensor or MAF sensor is bad, it could give incorrect data to your engine’s computer, causing a misfire.

How do I know if I have a bad coil pack?

  1. Rough idling
  2. Louder noise from the engine than usual.
  3. Poor engine performance.
  4. A reduction in the engine speed
  5. Check engine light illumination
  6. Poor fuel economy
  7. Difficult to start the vehicle
  8. Jerking and vibrating acceleration
  9. Engine stalling

Can a bad catalytic converter cause a misfire?

A bad catalytic converter causes fuel within your engine cylinder to heat up to the point that it actually ignites. This ignition is what causes the misfiring sensation, which may badly damage your engine parts.  

Read More
  1. P0300 Code Meaning and Causes
  2. P0301 Code Meaning and Causes
  3. P0303 Symptoms and Causes
  4. P0304 Code Symptoms and Causes
  5. P0191 Code Symptoms and Causes

Leave a Comment