P0354 OBD-II Trouble Code: Ignition Coil D Primary / Secondary Circuit Malfunction

P0354 code definition

When there is a problem in the ignition coil “D” circuit (on either the primary or secondary side), the P0354 code will be stored. For the vehicle to run smoothly and without stalling, it’s essential for the ignition coil (or coils) to perform properly. If they are not, you can expect a P0354 code to be stored and the Check Engine Light or MIL (Malfunction Indicator Light) to illuminate.

What the P0354 code means

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.

What causes the P0354 code?

Several issues can cause a vehicle’s powertrain control module (PCM) to store a P0354 code. Some of the most common causes include:

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

What are the symptoms of the P0354 code?

Unlike some other codes, when the P0354 code is stored, you will almost always notice more symptoms than the Check Engine light illuminating. In addition to this (or the MIL illuminating), common symptoms include:

• Misfiring engine (may be consistent or intermittent.)
• Rough engine idle
• Misfiring when accelerating

In some rare cases, you may not notice any symptoms besides the Check Engine light coming on.

How does a mechanic diagnose the P0354 code?

When the P0354 code is stored, it indicates that the PCM is not receiving the proper signals from the ignition coil(s) when the vehicle is in operation. This can be indicative of problems with either the primary (computer) side of the ignition coil or the secondary (spark plug) side of the coil.

Verifying the cause of the code will require an OBD-II scanner and several tests. A test drive to attempt to reproduce the situation in which the code was stored can also be helpful, so 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, and the mechanic can continue with diagnostic steps to determine the cause of the problem, fix it, clear the code, and retest it.

Common mistakes when diagnosing the P0354 code

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 was a leak in the vacuum. Likewise, some people will assume that the spark plugs need to be replaced when the problem is with a vacuum leak or some other cause.

How serious is the P0354 code?

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.

What repairs can fix the P0354 code?

Some of the most common repairs for a P0354 code include:

• 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)

Additional comments for consideration regarding the P0354 code

In addition to making driving unpleasant and potentially unsafe, a stored P0354 code can make it difficult to renew your vehicle’s registration. In order to pass an OBD-II emissions test, you cannot have an illuminated Check Engine Light or MIL, and one of these lights will continue to be illuminated until you solve the problem and clear the code.

Need help with a P0354 code?

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