P0351 Code Meaning, Causes, Symptoms, And How To Fix

The ignition coil is one of the major parts of your vehicle. The ignition coils are most commonly used in gasoline engines. The main function of the ignition coil is to take high voltage current from the vehicle battery and deliver it to the spark plug. The diagnostic trouble code (DTC) P0351 indicates a problem with your ignition coil. This article mainly explains the P0351 code symptoms and causes.

P0351 Code Definition

The P0351 code indicates “Ignition Coil “A” Primary/Secondary Circuit Malfunction.”

The ignition coil of your vehicle contains a “primary” winding and a “secondary” winding. A switching device is used to trigger the primary winding so that the secondary winding generates the needed high-voltage spark.

What Does the P0351 Code Mean?

The P0351 code indicates that the powertrain control module (PCM) detects an issue with the cylinder #1 ignition coil or its circuit.

P0351 Code

The ignition coil works like a transformer. It contains two coils. It takes electric current from your car battery, transforms it into high voltage, saves it briefly, and then emits it as a high voltage current pulse to the spark plug.

The spark plug uses the high voltage current delivered by the ignition coil to generate the spark. The spark generated by the spark plug is used to burn the air-fuel mixture in the combustion chamber.

Because the PCM energizes the primary side of each coil or pair of coils, the voltage generated by the primary winding may spike each time the secondary winding is energized if the PCM does not detect a primary voltage spike, it means that there is something wrong with the primary and secondary components of the coil or coil pack.

If the secondary element of the ignition coil is short-circuited, the primary spike will be damped accordingly. When your PCM detects a problem with your ignition system, it triggers the P0351 code to alert the driver.

Causes of P0351 Code

The P0351 engine code is triggered due to one or more of the following causes:

  • Faulty ignition coil
  • Poor electrical connections
  • Bad spark plug
  • Open or short in the ignition coil wiring harness
  • Damaged or corroded spark plug wiring
  • Vacuum leaks
  • Carbon buildup in the throttle body
  • Bad PCM

Symptoms of P0351 Code

A vehicle with P0351 trouble code produces one or more of the following symptoms:

  • Illuminated check engine light
  • Engine misfiring
  • The vehicle is difficult to start
  • A reduction in engine power
  • Poor fuel economy
  • Poor acceleration  
  • Rough or erratic idle

How to diagnose the P0351 Code?

Follow the following steps to diagnose the P0351 engine code:

  • Uses an OBD-II scan tool to ensure the existence of the P0351 code in the PCM.
  • Use the freeze frame data to check what’s going on. Continue the troubleshooting based on the other trouble codes you may find.
  • Clear the codes and take your car for a test drive. If the trouble code returns, then perform a deep inspection.
  • Visually inspect the wiring and connections of the coil system.
  • Inspect the coil pack of your car.
  • Inspect the spark plug. If your spark plug is faulty, then replace it.
  • Use a vacuum gauge to check the vacuum leaks. A vacuum leak is one of the major reasons of an engine misfire.
  • Properly inspect the primary ignition coil. If the coil is damaged, replace it.
  • Perform a compression test to test the compression system of the engine.
  • Measure the resistance of the ignition coil by using a multimeter. Compare the readings written on the vehicle’s service manual.  
  • Remove the cylinder #1 ignition coil and install it on cylinder #2. If your vehicle triggers the P0352 code, it means your ignition coil is faulty and you need to replace it.
  • Test the PCM if no fault has been found up until this point.

Common P0351 Code Diagnostic Mistakes

  • Replacing the components without testing
  • Replacing the unnecessary parts
  • Overlooking the vacuum leaks
  • Replacing the spark plug or ignition coil without inspecting the wiring or connections

P0351 Code Repair Cost

The repair cost of the P0351 code varies according to labor cost, the vehicle model, and the nature of the repair. To fix the P0351, you may need one or more of the following repairs:

Ignition coil replacement$160 to $220
Vacuum leak repair$70 to $380
Spark Plug replacement$60 to $260
PCM replacement$240 to $3,000

How serious is the P0351 code?

The P0351 code is considered a serious trouble code. This stems from the fact that a number of relatively severe drivability-related symptoms often accompany this DTC. As a result, you could be left stranded if your vehicle did not start, or could find yourself in a dangerous situation, should your car stall while in transit.

Additionally, prolonged issues of this type can lead to downstream catalyst damage. While some vehicles deactivate the fuel injector, which corresponds to the affected cylinder, others do not.

This causes unburned fuel to be dosed downstream into a vehicle’s catalytic convertor. This fuel allows the superheating of the catalytic converter to occur, thus resulting in severe and costly damage.

What repairs can fix the P0351 code?

To fix the P0351 engine code, you need to repair one or more of the following parts:

  • Replacing the faulty spark plugs
  • Replacing the bad throttle body
  • Cleaning the clogged throttle body
  • Repairing or replacing the damaged spark plug wiring
  • Repairing the wiring harness
  • Replacing the faulty ignition coil
  • Replacing or reprogramming the PCM
  • Repairing the damaged electrical connections

How To Prevent P0351 Code From Triggering?

  • Replace your vehicle’s spark plug according to the manufacturer’s recommendations
  • Replace the ignition coil according to the manufacturer’s recommendations
  • Always use quality parts while replacing the old parts
  • Use high-quality fuel with the correct octane rating
  • Don’t overload your engine
  • Keep your car’s battery in good condition
  • Ensure maintenance of your vehicle according to the manufacturer’s recommended schedule and guidelines

FAQ Section

Where is the ignition coil located?

The ignition coil is installed in between the battery, and if the vehicle is old, the distributor that distributes the HT voltage it produces to each spark plug via thick rubbery HT leads (one per plug). The ignition coil takes electric current from your car battery and transforms it into high voltage, saves it briefly, and then emits it as a high voltage current pulse to the spark plug.

How do I know if my ignition coil is bad?

When the ignition coil goes bad, it generates one of the below-given symptoms:

  • Misfiring
  • Loss of Power
  • Higher consumption of fuel
  • Check engine light illumination
  • Backfiring
  • The vehicle is hard to start
  • Spluttering and Coughing Sounds
  • Engine stalling
  • Jerking acceleration

What are primary and secondary ignition?

The primary circuit is installed between the ignition coil and the battery. The secondary circuit is installed between the spark plug and the ignition coil.

Can I drive with the P0351 code?

Yes, you can drive with P0351 for a short distance. However, it is not recommended to drive for a long time with this code. Driving with P0351 is very dangerous. This code generates multiple drivability symptoms that will not make it safe to drive. This code may generate engine stalling issues or make your vehicle hard to drive.  

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