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P0312 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


Understanding Diagnostic Trouble Codes (DTC) is essential for maintaining your vehicle’s 

health. One such code that can be found on your vehicle’s diagnostics system is P0312. The definition, meaning, causes, symptoms, diagnosis, common errors, and possible corrections associated with P0312 will be explored within the context of this Comprehensive Guide. To begin, let us decipher what P0312 means.


To fully grasp P0312, let’s break down its meaning:

  • “P” stands for Powertrain, indicating that the issue affects the engine and transmission.

  • “0” denotes a generic code that applies to all vehicle makes and models.

  • “3” specifies that it’s a misfire code.

  • “12” identifies the specific cylinder where the misfire is detected, in this case, cylinder number 12.

In essence, P0312 informs you that there’s a misfire occurring in the twelfth cylinder of your engine.


Let’s now investigate the typical causes of P0312:

  • Ignition System Issues: Misfires in a particular cylinder might be caused by ignition system issues, such as a broken spark plug or ignition coil.
  • Fuel Delivery Issues: A misfire may occur if there is insufficient fuel delivered to cylinder 12.
  • Vacuum leaks: The air-fuel combination can be messed up by leaks in the intake manifold or vacuum lines, which can result in misfires.
  • Sensor issues: Defective sensors, such as the Mass Airflow Sensor (MAF) or the Crankshaft Position Sensor, might send the engine control module the wrong information, which can lead to misfires.


  • P0312-related problems can appear in many different ways, including:
  • Check Engine Light: The check engine light on your dashboard turning on is the most typical sign.
  • Rough Idling: If you see your car idling roughly, it often means there was a cylinder misfire.
  • Reduced Power: Engine misfires may significantly lower the power and overall performance of an engine.
  • Increased Emissions: Prolonged misfires can result in higher emissions, which may affect your vehicle’s compliance with emissions standards.


It’s critical to use a methodical diagnostic approach when dealing with a P0312 code:

  • Code Scan: Start by retrieving the code and learning its specifics using an OBD-II scanner.
  • Visual Inspection: Look for wear or damage on the spark plugs and ignition coils that are part of the ignition system.
  • Check the fuel system: Make that the fuel delivery system is operating properly by testing the fuel pressure and injectors.
  • Sensor evaluation: Check the accuracy of important sensors, such as the MAF sensor or the crankshaft position sensor.

Common mistakes

Some frequent errors to avoid when diagnosing and fixing P0312 are as follows:

  • Misfires can result from neglecting basic maintenance, which includes changing spark plugs at the proper intervals.
  • Replacing components without doing enough testing could result in time and financial waste.
  • ignoring other relevant codes or problems, since misfires may occasionally be a sign of deeper difficulties.

How serious is this?

The seriousness of a P0312 code depends on several factors, including the underlying cause and the extent of the misfire. Despite being an emergency, ignoring this code may lead to a decrease in engine performance, increased emissions, and permissions, and age of the catalytic converter over time. To avoid any more problems, immediate diagnosis and correction are advised.

What repairs can fix the codeS?

repair manuals

The repairs needed to address P0312 will depend on the specific cause but may include:

  • Replacing faulty spark plugs or ignition coils.
  • Addressing fuel delivery issues, such as clogged fuel injectors or a failing fuel pump.
  • Fixing vacuum leaks in the intake system.
  • Replacing malfunctioning sensors that contribute to the misfire.

Related codes

P0312 may be associated with other related codes, such as:

  • P0300: “Random/Multiple Cylinder Misfire Detected,” which indicates misfires occurring in multiple cylinders.
  • P0301, P0302, P0303, etc.: These codes specify misfires in individual cylinders, with the last digit indicating the cylinder number (e.g., P0301 for cylinder 1 misfire).


P0312 is the diagnostic error code that indicates failure in a particular cylinder of your engine, for example, Cylinder 12, that we are referring to. For effective management of this problem, we need to understand its meaning, causes, symptoms, and diagnosis process. It can help to improve the vehicle’s performance and avoid any potential damage by diagnosing it correctly and performing appropriate repairs.

P0312 Code – What Does It Mean & How To Fix It