Maintenance Tips, Tricks And Hacks For Your Vehicle

P0351 OBD-II Ignition Coil A Primary/Secondary Circuit Trouble Code




The P0351 is an OBD-II Trouble Code that stands for “Ignition Coil” A” Primary/Secondary Circuit Malfunction and is triggered when the ignition coil on cylinder #1 is not working properly.

The vehicle’s ignition coil consists of a “primary” winding and a “secondary” winding. A switching device is used to activate the primary winding in order for the secondary winding to produce the required high-voltage spark.

In this article, I will explain everything you need to know about the P0351 code.

What Does The P0351 Code Mean?

P0351 OBD-II Ignition Coil A Primary Secondary Circuit Trouble Code

The P0351 code means that the powertrain control module (PCM) has detected a possible issue with the cylinder #1 ignition coil or its circuit.

The ignition coil functions similarly to a transformer. It contains 2 coils. It takes current from your car’s battery, converts it to high voltage, temporarily stores it, and then emits it as a pulse of high-voltage current to the spark plug.

The spark plug generates the spark using the high-voltage current supplied by the ignition coil. The air-fuel mixture in the combustion chamber is ignited by the spark produced by the spark plug.

Because the PCM energizes the primary side of each coil or set of coils, the voltage generated by the primary winding may surge whenever the secondary winding is powered. If the PCM does not detect a primary voltage spike, there is a problem with the primary and secondary components of the coil or coil pack.

If the second element of the ignition coil is short-circuited, the primary spike will be correspondingly attenuated. The P0351 code is triggered when the PCM detects a problem with the ignition system.

(See also: P0300 OBD-II Random/Multiple Cylinder Misfire Detected Trouble Code)

Which Models Are Affected By The P0351 Code

MakeAffected By P0351 Code

What Are The Possible Causes of the P0351 Code?

The P0351 code is caused when the vehicle’s computer detects an issue with the cylinder #1 ignition coil or its circuit.

There are a number of potential underlying causes for diagnostic trouble code P0351, some of which are easier to identify than others. Understanding each of these potential root causes facilitates the diagnosis of your vehicle’s problems.

Here are the most possible causes of the P0351 code:

  • Inoperable or fouled spark plugs
  • Defective plug wires
  • Faulty ignition coil
  • Loose electrical connection
  • Faulty ignition circuit wiring
  • Vacuum leak Intake/ EGR (exhaust gas recirculation) faults
  • Faulty ECM (engine control module)

(See also: P0401: EGR Flow Insufficient Detected – Meaning, Symptoms, Causes, and How To Fix It)

What Are The Common Symptoms of The P0351 Code?

P0351 diagnostic trouble code is associated with a variety of symptoms, some of which tend to be more severe than others. If you can spot each of these symptoms, it will be easier to figure out what’s wrong.

Below are the most common symptoms associated with the P0351 error code:

  • Illuminated check engine warning light
  • Engine misfiring
  • The vehicle is hard to start.
  • Reduced engine power
  • Reduced fuel economy
  • Sluggish acceleration
  • Unsteady or erratic idle

Is It Safe To Drive With a P0351 Code

It is not safe to drive with a P0351 code because it means that one of the cylinders is not working properly. Depending on the severity of the associated symptoms, the P0351 code may result in unsafe driving conditions.

While driving with a P0351 code, you can expect the car to shake, misfire, lack of power, and burn too much gas.

This code shouldn’t stop the car from being driven to a safe place, but it should be fixed as soon as possible so that it works as it should.

How To Diagnose The P0351 Code

Here is how to diagnose the P0351 code:

  1. Using an OBD-II scanner, check the codes saved in the PCM.
  2. Check out what’s going on by looking at the freeze frame data. Continue fixing the problem based on any other error codes you find.
  3. Get rid of the codes.
  4. Test drive your vehicle. If the P0351 code comes back, move on to the next step.
  5. Check the coil system’s wiring and connections visually.
  6. Check out the coil pack on the car.
  7. Check the plug’s spark plug. If your spark plug is faulty, you should get a new one.
  8. Check for vacuum leaks with a vacuum gauge. One of the main things that can cause an engine to misfire is a vacuum leak.
  9. Check the primary ignition coil the right way. If the coil is damaged, you should replace it.
  10. Do a compression test on the engine to check its compression system.
  11. If no problem has been found up to this point, test the PCM.

This code should be thoroughly investigated. Replacing components without testing or bypassing diagnosis stages may result in the return of the error code. A basic component, such as a loose or bent connector pin, could nonetheless cause problems.

(See also: P2195 OBD-II O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 1 Trouble Code)

Most Common Mistakes When Diagnosing The P0351 Code

The most common mistakes when diagnosing the P0351 code are:

  • Replacement of the components without testing
  • Replacement of the unnecessary parts
  • Changing the spark plug or ignition coil, without checking the wiring or connections

How Much Does It Cost To Repair P0351 Code

MakeP0351 CodeRepair Cost
ToyotaYes$22 – $73
NissanYes$22 – $73
ChevroletYes$22 – $73
BMWYes$22 – $73
AudiYes$22 – $73
BuickYes$22 – $73
MercedesYes$22 – $73
GMCYes$22 – $73
SuzukiYes$22 – $73
TataYes$22 – $73
LexusYes$22 – $73
MazdaYes$22 – $73
MitsubishiYes$22 – $73
KiaYes$22 – $73
JeepYes$22 – $73
FiatYes$22 – $73
HondaYes$22 – $73
HyundaiYes$22 – $73
OpelYes$22 – $73
FordYes$22 – $73
FiatYes$22 – $73
PeugeotYes$22 – $73

What Repairs Can Fix The P0351 Code

Repairs that can fix the P0351 code include:

  • Replacing the defective spark plugs
  • Changing out the throttle body
  • Replacing or repairing faulty spark plug wiring
  • Repairing the wiring harness
  • Replacing the defective ignition coil
  • Reprogramming or replacing the PCM (powertrain control module)
  • Repairing the faulty electrical connections

How To Fix The P0351 Code

The following steps can be utilized to assist in resolving the cause of the P0351 DTC on your vehicle. Before attempting such repairs, it is always strongly recommended that you study the manufacturer-specific service manual for your vehicle.

Here is how to fix the P0351 code:

  • Replace the faulty ignition coil
  • Replacing or repairing an ignition coil connector
  • Repair any other electrical wiring or connectors faults
  • Replacing the spark plug and spark plug wire
  • Replace the throttle body
  • Replace or repair the PCM

In Conclusion

There are numerous causes for the P0351 code, and a faulty ignition coil should not be neglected for too long. Remember that your engine is the heart of your car, thus any engine issues, such as a shorted coil driver circuit, a damaged fuel injector, or a defective fuel pump, should always be handled by a professional.



Vide Polowenski, Senior Mechanic

The information in this article is current and up-to-date in accordance with the latest mechanic SOPs.

Please take the time to leave a comment if this article has helped you in any way, you need additional help, or you have a suggestion.

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