P0300 Diagnostic Trouble Code

Published: March 25, 2022

If you're dealing with a P0300 error code, brace yourself for a lengthy diagnostic and repair process. This code confirms what we already know — the engine has poor performance. "Random or Multiple Cylinder Misfire Detected" is the meaning of the code P0300. This diagnostic trouble code (DTC) suggests that the computer in your vehicle has spotted an engine misfire.

A P0300 code may indicate something amiss with the fuel mixture, compression, or spark within the cylinders, and if not addressed immediately, the engine or catalytic converter may sustain significant damage.

What Does A P0300 Code Mean?

When the quantity of gas burning in the cylinder is insufficient, your engine will misfire. Sufficient fuel combustion is critical for the engine to operate optimally, as the energy released by the burning fuel powers the engine.

P0300 is a diagnostic code that indicates single or multiple misfires. However, a P0300 does not indicate which cylinder(s) is/are misfiring or why. Along with P0300, you're likely to see another OBD-II code ranging from P0301 to P0308. If the final digit is not zero, it indicates which cylinder is misfiring. 

This code will illuminate your check engine light and must be corrected immediately. If ignored, you will most likely need to replace the catalytic converter and diagnose the other component causing the misfire.

There are numerous possible causes of this OBD code. Because it is a "random misfire" or "multiple misfire," it means that the misfire occurs on multiple cylinders rather than just one.

Common Symptoms of P0300 Code

If your vehicle has the trouble code P0300, you may experience one or more of the following symptoms:

  • Weak acceleration
  • Jerking during acceleration
  • Engine not starting
  • Difficulty to start the engine
  • Car shakes and vehicle runs erratically
  • Increased consumption of fuel
  • Exhaust smells of fuel
  • Check Engine Light is illuminated

How To Fix P0300 Code

If your car is misfiring and you are unsure about diagnosing the problem yourself, we recommend contacting a licensed mechanic who can pinpoint the issue and provide an accurate car repair cost.

To diagnose, fix, and maintain your car, you will need vehicle-specific diagnostic and repair information. However, here are some things you can do independently to narrow down the issue.

Check Ignition Connectors

Conduct a visual inspection of the engine for any loose or broken connectors, particularly the ground wires. These issues can result in random misfires. Where necessary, tighten, connect, or replace parts.

Examine Spark Plugs

The most likely cause of random misfires is broken or worn spark plugs. If necessary, start by replacing the spark plugs and wires and then re-test for misfires.

Examine Fuel System

If your ignition system is working normally, check to see if the random misfires are being caused by a problem with your fuel system. Inspect if your engine is receiving a sufficient amount of fuel to operate properly.

Inspect Fuel Level Pressure

Low fuel pressure results in sporadic engine cylinder misfires. When an engine receives insufficient fuel, it begins to misfire. Low fuel pressure could be caused by the fuel pump or the fuel pressure regulator.

Conduct an engine compression and leak-down test

Perform an engine compression test and a leak-down test after verifying that the ignition and fuel systems are operational. This will indicate whether any mechanical issues are to blame for your misfires.

How Serious Is A P0300 Diagnostic Trouble Code?

Code P0300 points to a very serious problem. Not only can it lead to dangerous driveability issues to occur, but also to an engine or catalytic converter damage.

In the event of a major misfire, the cylinder's power contribution may be negligible, leading to low engine power. As a result, the remaining cylinders must work hard to fulfill the vehicle's power requirements. This could result in an increase in fuel consumption and mileage.

Neglecting this error may result in an overheated exhaust and a melted catalytic converter. A damaged catalytic converter increases the engine's back pressure, resulting in unsecure or risky operating conditions.


Since the error can be caused by a variety of factors, determining the root cause can be challenging. This frequently results in a lengthy and arduous process of repairing code P0300. At other times, this code may be triggered by multiple issues.

For more recommendations on auto repair and maintenance, head over to KeepDriving today!

Founder, Editor-in-Chief Carmelo Pickel is the Founder and Editor-in-Chief of Keep Driving, with almost 20 years of experience working in the industry. Before founding Keep Driving, Carmelo held leadership roles for over a decade on top automotive dealership corporations across North America, handling various leadership roles in Sales, Marketing, and Incentives.
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