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P0356 OBD-II Trouble Code: Ignition Coil F Primary/Secondary Circuit Malfunction

Check Engine Light

P0356 code definition

The P0356 trouble code identifies that the ignition coil F primary/secondary circuit is malfunctioning.

What the P0356 code means

If a vehicle is modern enough to feature a PCM (Powertrain Control Module), then it’s definitely using a COP (Coil on Plug) ignition system. With a COP, each of the vehicle’s cylinders has its own coil. These coils are all controlled by the PCM which attaches to each with two wires. One of these wires is used as a battery feed and the other is the coil driver circuit. The PCM ungrounds and grounds this circuit to deactivate or activate the coil.

Amongst other things, this setup makes spark plug wires unnecessary. Instead, the coils sit right above their spark plugs. However, a COP is definitely not without its potential for problems.

P0356 is stored when the PCM detects an open or short with the driver coil dedicated to coil #6. In some vehicles, the PCM will actually go ahead and shut down this coil’s fuel injector to prevent further damage.

What causes the P0356 code?

A vehicle’s PCM could log a P0356 code for a handful of reasons:

  • The (COP) could simply be faulty
  • Coil #6 could have a loose connection
  • Coil #6’s connector locks could be broken
  • The COP driver circuit is open
  • The COP driver circuit has a short to voltage or is ground

If none of these proves to be responsible, there’s always the unlikely chance that the problem is simply a PCM that isn’t working correctly.

What are the symptoms of the P0356 code?

There are two main symptoms that generally accompany this code. The first is that the engine is misfiring. Another indicator would be that the engine performance may be intermittent.

Usually, the Check Engine light will be immediately triggered when this code is registered, but some models may wait until several incidents before this happens or the code is logged.

How does a mechanic diagnose the P0356 code?

A mechanic will begin the diagnosis process by using an OBD-II scanner to download all the codes that have been stored. Next, they’ll check on the ignition coil and the ignition coil driver circuit. Any of the wires running into the PCM will have to be examined too. Finally, they’ll examine the connector to look for signs of corrosion or other types of damage.

Common mistakes when diagnosing the P0356 code

A lot of times, mechanics will rush to carry out a maintenance tune up. Although the vehicle may benefit from such a procedure, it won’t make the P0356 code clear. Unfortunately, a comprehensive diagnosis must be undertaken to truly pinpoint the problem (or problems) triggering this code.

How serious is the P0356 code?

The problems associated with the P0356 code aren’t serious enough that it represents a threat to life, but it can evolve into something that demands more expensive repairs if not seen to right away. If nothing else, the owner will have to spend a lot more money at the pump because of an engine that is underperforming.

What repairs can fix the P0356 code?

Generally, the repairs necessary to clear this code are simple. They will involve one of the following:

  • Repairing or replacing the ignition coil
  • Repairing or replacing a shorted or open wire in the ignition coil driver circuit
  • Cleaning, repairing, or replacing the connector if corrosion has damaged it

Additional comments for consideration regarding the P0356 code

A lot of times, mechanics will find open circuits in the ignition coil circuit on top of the engine. This is a telltale sign that the damage was caused by wildlife that got under the hood. Usually, this happens in cold environments when the vehicle is parked outside. While the engine is still warm from use, rodents will climb inside and, often, chew through wires.

Need help with a P0356 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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