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An on-board diagnostic or OBD-II code helps you or your mechanic identify potential issues in your vehicle. But to resolve the code, you must first know what issue has caused it to be set in the system. If you’re having trouble figuring out what code P0356 means, you’ve come to the right place. Read on to learn about its possible triggers and common symptoms.

What Does the P0356 Code Mean?

Diagnostic trouble code (DTC) P0356 stands for “Ignition Coil F Primary/Secondary Circuit Malfunction.” It is logged once the powertrain control module (PCM) detects that the ignition coil is unresponsive. 

Modern engines use an electric ignition system called coil-on-plug (COP). In a coil-on-plug system, there is one ignition coil for each cylinder. Each COP coil sits directly on top of a spark plug. These coils are controlled and monitored by the PCM. 

removing ignition coil from spark plug
In a coil-on-plug system, there is one ignition coil for each cylinder.

The ignition coil is the core of any ignition system. Through electromagnetic induction, it creates a high-voltage spark that the ignition system needs to function. It is also responsible for igniting the mixtures inside the engine’s combustion chambers. If it fails, the engine could misfire.

There are two primary types of COP coils: two-wire and three-wire coils. The two-wire design has one wire that serves as a battery feed and another that is a coil driver circuit from the PCM. The PCM controls this circuit to trigger the deactivation or reactivation of the coil. It also monitors this circuit for any defects.

If the PCM perceives a possible problem in one of the coils or if it loses control of the circuit, it logs error code P0356.

Some vehicle models are more prone to code P0356 than others. Have a technician check your vehicle immediately if you own a Ford (especially Ford F-150), Toyota, Lincoln, Mercedes Benz, or Lexus and your diagnostics show P0356.

Note: The definition of code P0356 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition. 

What are the Possible Causes of the P0356 Code?

P0356 is a generic code, so it can have several triggers. Here are the most common:

  • Defective ignition coil
  • Wiring issue
  • Poor connection 
  • Faulty PCM

What are the Common Symptoms of the P0356 Code?

You may notice the following symptoms if your vehicle has logged the code P0356:

  • Check engine light is active
  • Poor engine performance
  • Engine misfire
  • Poor fuel mileage
closeup of modern automobile engine
Engine misfire is a common symptom of code P0356.

How to Diagnose the P0356 Code

Prevent further complications by addressing an engine code P0356 right away. However, obtaining an accurate diagnosis can prove difficult as the code shares common triggers and symptoms with other DTCs. All vehicles are built differently, so the diagnostic steps will also vary depending on their manufacturer. 

For instance, the procedure for diagnosing a P0356 on a Toyota may be different from testing for the same code on a Ford. For the appropriate steps, always consult your vehicle’s repair manual. If you decide that DIY auto repair is not for you, you can always seek the help of a mechanic.

How to Fix the P0356 Code

Code P0356 may be logged in vehicles of varying makes and models, so you should always refer to repair information specific to your vehicle for the appropriate repair steps. If you aren’t confident in your automotive know-how, it may be best to leave the job to a mechanic.
However, if you’re set on resolving this code on your own, make sure your automotive knowledge is up to date. Refer to a repair manual or an online repair database to learn how to resolve code P0356.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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