P0355 OBD-II Trouble Code: Ignition Coil B Primary/Secondary Circuit Malfunction

P0355 code definition

When the PCM (powertrain control module) identifies an electrical malfunction in ignition coil B’s primary or secondary circuit, it will set code P0355 to indicate the problem. The Check Engine Light will then illuminate.

What the P0355 code means

The engine’s ignition coils’ job is to ignite the air/fuel mix in each of the engine’s combustion chambers. When one of these ignition coils (in this case, coil B) has an electrical problem, the engine will not be able to run smoothly, and it may hesitate or misfire.

What causes the P0355 code?

The most common causes of the P0355 code include:

• A defect or fault in ignition coil B
• One or more defective spark plugs
• An open or shorted circuit in the ignition coil
• A poor connection to the ignition coil
• Built-up carbon in the engine’s air passageways or the throttle body
• A faulty electronic body or idle air control valve

What are the symptoms of the P0355 code?

There may be a number of symptoms associated with a P0355 code, including:

• The Check Engine Light will come on
• The engine will lose power or present a general lack of power when accelerating
• The engine will hesitate when accelerating
• The engine’s idle will be noticeably rougher
• The vehicle will be difficult to start

How does a mechanic diagnose the P0355 code?

After identifying the P0355 code and any other stored codes from the PCM, using an OBD-II scanner, the mechanic will start by visually inspecting the wiring and circuits connected to ignition coil B. They will then pay close attention to the crank signal, as a problem here can cause numerous other issues, including a P0355 code.

After testing any repairs up to this point, they will switch the coil and its spark plug with the coil and spark plug from a good cylinder. Then they’ll clear the code and go for a test drive. If the PCM records a code for the ignition coil in the new cylinder, the mechanic will know that the problem is either with the spark plug or the coil and will test each to see where the issue is originating from. Then they’ll take steps to resolve the code and retest it once more.

Common mistakes when diagnosing the P0355 code

Sometimes the problem may actually be a leaking vacuum, rather than an issue with the ignition coil and/or spark plug. Replacing these without thoroughly inspecting the system can lead to an ineffective repair.

How serious is the P0355 code?

This code can significantly affect the drivability of the vehicle. If it’s left unresolved, it may also result in further engine damage and more expensive repairs down the road.

What repairs can fix the P0355 code?

The most common repairs for a P0355 code are:

• Replacing one or more faulty spark plugs
• Replacing ignition coil B
• Repairing or replacing the wiring harness for the ignition coil and/or other wires or connectors in the circuit
• Cleaning out built-up carbon from the engine’s air passageways or from the throttle body
• Replacing the idle air control valve and/or the electronic body

Additional comments for consideration regarding the P0355 code

It’s very important that you get your P0355 code resolved and cleared as soon as possible. This kind of problem may have a quick and inexpensive fix, but it can result in major engine problems and/or very dangerous situations in the future. And, if you do not get the problem resolved, the Check Engine Light will remain illuminated, and the vehicle will be ineligible to pass an OBD-II emissions test when you need to register it to drive legally in your state.

Need help with a P0355 code?

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