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P0354 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.

Definition

A P0354 trouble code on your OBD II scanner is defined as “Ignition Coil D Primary / Secondary Circuit Malfunction.”

Meaning

A P0354 code means that the ignition coil or coils are not functioning properly and that there is an electrical problem with them. The ignition coils are responsible for properly igniting the air-fuel mixture in the engine’s combustion chambers. If a vehicle has a P0354 code stored, it will not be able to ignite that mixture with the correct timing, and the engine will run roughly and/or stall.

Causes

There are a number of causes that can contribute to a P0354 trouble code appearing on your OBD II scanner: 

  • A leaking manifold vacuum. 
  • Defective ignition coil(s). 
  • A faulty idle air control valve. 
  • A faulty electronic body. 
  • One or more defective spark plugs.

Symptoms

There are several symptoms that you will notice with a vehicle that is experiencing a P0354 trouble code: 

  • The engine may be misfiring (maybe consistent or intermittent.).
  • The engine may have a rough idle. 
  • The engine may misfire when accelerating. 

Diagnosis

Here are the most rational steps that you can take when you are working through diagnosing a P0354 trouble code. When the P0354 code is stored, it indicates that the PCM is not receiving the proper signals from the ignition coil(s). This is when the vehicle is in operation. This can be indicative of problems that you are having with either the primary (computer) side of the ignition coil or the secondary (spark plug) side of the coil.

You will need to verify the cause of the code with an OBD-II scanner. You will also need to perform several tests to properly verify the code. First, you will need to take the vehicle for a test drive. This will serve as an attempt to reproduce the situation in which the code was stored. This can also be helpful in diagnosing the performance of the vehicle, as long as the mechanic pays close attention to the throttle position, engine cadence (RPMs), road speed, and engine load. If the vehicle is misfiring, the code will generally be verified. In this case, the mechanic can continue with diagnostic steps to determine the cause of the problem, fix it, clear the code, and retest it.

Common mistakes

One of the most common mistakes when diagnosing the cause of a P0354 code is diagnosing a defective ignition coil when the actual cause of the problem is a leak in the vacuum. Likewise, some people will assume that the spark plugs need to be replaced when the problem has to do with a vacuum leak or some other cause.

How serious is this?

In most cases, when a P0354 code is stored, the vehicle will run rough and either intermittently or consistently misfire when accelerating. These symptoms can be unpleasant at best and dangerous at worst. Consider what might happen if you need to accelerate quickly but your vehicle is misfiring and not behaving as it should. This can lead to serious problems, which is why we recommend that you get this code diagnosed and repaired immediately. 

What repairs can fix the code?

There are a few repairs that fix this trouble code: 

  • Replacing or repairing a leaking manifold vacuum. 
  • Replacing faulty wiring to the ignition coil(s). 
  • Replacing old or mismatched spark plugs. 
  • Replacing or repairing the ignition coil(s). 

Related codes

None listed.

Conclusion

Though this trouble code does not have severe ramifications that can appear immediately, it is a serious problem that the driver and a mechanic should address as soon as possible. The problem indicated by this code can be not only harmful to the car, but to the driver as well. In serious cases like these, engine misfires can lead to dangerous, harmful, and even fatal accidents. As such, if you are experiencing any of these symptoms and are able to properly test and diagnose the code, this is something that should be fixed and corrected immediately.