P0355 Code: Ignition Coil “E” Primary/Secondary Circuit

There are three things needed to start the combustion process in a gas-powered engine: an air/fuel mixture, compression, and an ignition source. The air intake system and the fuel delivery system are responsible for the air and the fuel, respectively. As for the ignition source, a vehicle relies on ignition coils and spark plugs to ignite the fuel and power the engine.

The P0355 code indicates that there is an issue with one of your ignition coils. What causes this trouble code and how should you resolve it? This short but informative guide will help you answer these questions and more.

What Does the P0355 Code Mean?

Diagnostic trouble code (DTC) P0355 stands for “Ignition Coil “E” Primary/Secondary Circuit.” It indicates that the powertrain control module (PCM) detected a problem in either the primary (computer side) or the secondary (spark plug side) #5 ignition coil “E” circuit.

To learn more about how the primary and secondary windings of ignition coils work, click here.

Ignition coils create the high voltage the spark plugs need to ignite the air-fuel mixture inside the combustion chamber. They are crucial in preventing stumbles and misfires.

Most vehicles nowadays use the coil on plug (COP) ignition system, which removes the need for spark plug wires and distributor caps. In this system, the ignition coil goes right above the spark plug, allowing the PCM to control the ignition circuit on each cylinder directly.

The PCM will set the P0355 code when it does not receive a proper pulse signal from the ignition coil. The PCM may also turn off the fuel injector to the cylinder with the malfunctioning coil circuit to mitigate the issue. It varies depending on the vehicle.

The short version is that the P0355 code appears when the powertrain control module (ECM/PCM), perceives a problem with the cylinder #5 ignition coil or its circuit.

The P0355 code appears when the powertrain control module (ECM/PCM), perceives a problem with the cylinder #5 ignition coil or its circuit.

–Richard McCuistian, ASE Certified Master Automobile Technician

You may also watch this video to understand how ignition coil works:

P0355 on Some Ford Vehicles

Each ignition primary circuit is continuously monitored. The test fails when the PCM does not receive a valid ignition diagnostic monitor (IDM) pulse signal from the ignition module (integrated in the PCM).

Code P0355 may appear on some Ford vehicles. On a 2008 Ford F-150 XL 4.2L V6, for example, this DTC can appear because of the following conditions:

• Open or short in the ignition START/RUN circuit
• Open coil driver circuit
• Coil driver circuit short to ground
• Damaged coil
• Coil driver circuit short to VPWR

For this specific vehicle, it is important to note that DTC P035x only sets for a coil primary circuit failure. A secondary ignition coil or spark plug failure does not set DTC P035x.

Note: The definition of code P0355 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 P0355 Code?

There are a handful of reasons the engine code P0355 may register in the vehicle’s memory. Take note that most OBD-II codes have multiple possible causes. Below are some of the most likely causes of this error code.

• Defective cylinder #5 ignition coil
• Ignition coil circuit issues (e.g., damaged wiring, loose connections, etc.)
• PCM issues (e.g., outdated software)

What are the Common Symptoms of the P0355 Code?

Problems with the ignition coils and ignition coil circuits typically cause problems with engine performance and drivability. Should you encounter this trouble code, it’s best to address the issue right away to prevent damage to your engine. Here are some of the most common issues associated with Code P0355 Ignition Coil E:

• Check Engine Light is on or flashing
• Engine idles rough
• Engine misfires may be present or intermittent 
• Lack of acceleration
• The engine may not exhibit noticeable symptoms (rare)

How to Diagnose the P0355 Code

To resolve the code P0355, you must determine its exact cause to reach an effective, long-term fix. Diagnosing OBD-II codes may be intimidating, but it is definitely possible.

Good thing there are a lot of repair resources nowadays, especially for DIYers. Aside from repair manuals and advice from your mechanic, there are also guides and video resources on the internet. Here is a helpful video resource you can use to learn more about the P0355 code:

How to Fix the P0355 Code

The exact steps to fixing the P0355 code will vary on a case-by-case basis. For example, ignition coils sit on top of the spark plugs. In comparison, coil packs require space for their bulk, so you can find them mounted on the engine, fender, or firewall. If you’re not sure about something, consult your owner’s manual or official repair manual.

Spark Plugs and Wiring

Bad spark plugs are a common reason for the P0355 code. They’re the first thing you should inspect.

Check the spark plugs for any issues. Their metal parts might have developed corrosion from exposure to leaded gasoline or other environmental factors. A plug might have also prematurely worn out from heavy use.

Aside from the spark plugs, you must also check the wiring harness that connects the plugs to the distributor or ignition coils. These wires are also susceptible to corrosion. They can also short, melt from the heat, or fray until they break. Damaged wires will prevent the spark plugs from operating properly.

If one of the spark plugs or its wires have failed, replace the bad part.

Ignition Coil Assembly E

Many vehicles have an ignition system with multiple direct coils. You must identify the specific coil that has developed an issue and replace the faulty part.

P0355 identifies transfer coil assembly E as the problematic part. You can test it by transferring the assembly to a good engine cylinder. Clear the trouble code and take the vehicle for a brief drive. Then check it with the scan tool again.

If the trouble code reappears on the previously operational cylinder that received ignition coil assembly E, the issue lies with the latter. Replace the bad ignition coil.

Ignition Coil Wiring

Additionally, inspect the wiring that connects the ignition coil pack to the distributor. Like the spark plugs and ignition coils, the wires can corrode, short, burn out, or fray. Bad wires prevent current from reaching the coils. If you find issues with the coil pack’s wiring, you must repair or replace the affected wires.

Vacuum Leaks

Vacuum leaks are one of the most common triggers of the P0355 code. When air leaks from the engine, it reduces the available oxygen and pressure. If you’re not careful, you might misdiagnose a vacuum leak as an issue with the ignition coil or spark plug.

Check the vacuum line, intake manifold gasket, and other parts for physical damage that lets air out. Some leaks can be repaired, but more severe cracks will require you to replace the bad part.

Powertrain Control Module

If the ignition coil, spark plugs, and cylinders are fine, the problem might lie with the PCM that controls the ignition process. The control module usually self-diagnoses and will set the related trouble code. There are occasions when the PCM fails to log a problem code, so you’ll have to test it.

After identifying, resolving, and repairing the issue that triggered the P0355 code, run a test again. If the trouble code doesn’t return, consider the diagnosis complete.

Where to Get New Ignition Coils for Your Car

Don’t expect great performance from your daily driver when it has logged a P0355 code. If you’ve determined that a bad ignition coil is the culprit, don’t put off getting a top-notch replacement from CarParts.com.

Find tailor-fit products in a few minutes and check out securely with a couple of clicks. Enter your vehicle’s year, make, and model into our vehicle selector to narrow the catalog to compatible ignition coils for your ride. We offer the best parts on our website, so you’re sure to get a top-notch ignition coil replacement tested by industry professionals.

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Don’t miss out on the best deals on the market, and shop for new ignition coils at CarParts.com today!

Products Mentioned in this Guide

Ignition Coil Spark Plug Wire Distributor Cap Fuel Injector