P0351 Malfunction of a primary / secondary circuit of the ignition coil

OBD-II Trouble Code - P0351 - Data Sheet

Ignition coil A primary/secondary circuit failure.

P0351 is a generic OBD2 Diagnostic Trouble Code (DTC) indicating a problem with ignition coil A.

What does trouble code P0351 mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles. Although general, specific repair steps may differ depending on the brand / model.

The COP (coil on plug) ignition system is what is used in most modern engines. Each cylinder has a separate coil controlled by the PCM (Powertrain Control Module).

This eliminates the need for spark plug wires by placing the coil directly above the spark plug. Each coil has two wires. One is battery power, usually from a power distribution center. The other wire is the coil driver circuitry from the PCM. The PCM grounds/disconnects this circuit to activate or deactivate the coil. The coil driver circuit is monitored by the PCM for faults.

If an open or short is detected in the coil driver circuit number 1, the P0351 code may occur. In addition, depending on the vehicle, the PCM may also disable the fuel injector going to the cylinder.

Symptoms

Symptoms of a P0351 trouble code may include:

• MIL Illumination (Malfunction Indicator Lamp)
• Engine misfires may be present or intermittent
• Engine is not working properly
• Car is hard to start
• Engine lacks power, especially under heavy load
• Irregular or unstable

Causes of the P0351 code

Possible causes of a P0351 code include:

• Short to voltage or ground in the COP driver circuit
• Open in COP driver circuit
• Bad connection on coil or broken connector locks
• Bad coil (COP)
• Defective transmission control module
• Faulty spark plugs or spark plug wiring
• Defective ignition coil
• Faulty or faulty ECU
• Open or short in coil harness
• Poor electrical connection

Possible solutions

Is the engine experiencing a malfunction now? Otherwise, the problem is most likely temporary. Try wiggling and checking the wiring on spool # 1 and along the wire harness to the PCM. If tampering with the wiring causes misfires on the surface, fix the wiring problem. Check for poor connections at the coil connector. Make sure the harness is not knocked out of place or chafing. Repair if necessary

If the engine is currently malfunctioning, stop the engine and disconnect the No. 1 coil harness connector. Then start the engine and check for a control signal on coil # 1. Using the scope will give you a visual reference to observe, but since most people don't have access to it, there is an easier way. Use a voltmeter on the AC hertz scale and see if there is a reading in the range of 5 to 20 Hz or so, indicating that the driver is working. If there is a Hertz signal, replace the # 1 ignition coil. This is most likely bad. If you do not detect any frequency signal from the PCM on the ignition coil driver circuit indicating that the PCM is grounding / disconnecting the circuit (or there is no visible pattern on the scope if you have one), leave the coil disconnected and check the DC voltage on the circuit driver on the ignition coil connector. If there is any significant voltage on this wire, then there is a short to voltage somewhere. Find the short circuit and repair it.

If there is no voltage in the driver circuit, turn off the ignition. Disconnect the PCM connector and check the integrity of the driver between the PCM and the coil. If there is no continuity, repair the open circuit or short to ground. If open, check the resistance between ground and the ignition coil connector. There must be endless resistance. If not, repair the short to ground in the coil driver circuit.

NOTE. If the signal wire of the ignition coil driver is not open or shorted to voltage or ground and there is no trigger signal to the coil, then a faulty PCM coil driver is suspected. Also be aware that if the PCM driver is defective, there might be a wiring issue that caused the PCM to fail. It is recommended that you perform the above check after replacing the PCM to ensure that it does not fail again. If you find that the engine is not skipping ignition, the coil is firing correctly, but the P0351 is reset continuously, there is a possibility that the PCM coil monitoring system may be malfunctioning.

HOW DOES A MECHANIC DIAGNOSTIC CODE P0351?

• Use a scanner to check which codes are stored in the ECU as well as freeze frame data for the codes.
• Clears codes and tests vehicle blocks in similar condition found in freeze frame data for best fault duplication.
• Performs a visual inspection of the coil system and its wiring for damaged or worn components.
• Use the scan tool to monitor data flow information and determine if the error occurs with a specific cylinder or with all cylinders.
• Inspect the spark plug wire and the vehicle's spark plug or coil pack if the problem is with only one cylinder.
• Check if the primary ignition coil is working properly if all cylinders are faulty.
• Checks the ECU if no faults have been found up to this point.

COMMON ERRORS WHEN DIAGNOSING CODE P0351

Mistakes are made when components are replaced without checking, or when all steps are not performed in the correct order. It's a waste of time and money for repairs.

HOW SERIOUS CODE P0351 IS?

Code P0351 may have some driving symptoms that make driving unsafe, depending on how severe the symptoms are. This code should not prevent the vehicle from moving to a safe location, but it should be corrected as soon as possible to ensure normal vehicle operation.

WHAT REPAIRS CAN FIX CODE P0351?

• Replacing Spark Plugs and Spark Plug Wiring
• Replacing the ignition coil
• Wiring repair
• Eliminate electrical connection error
• Replacing the control unit

How to Fix P0351 Engine Code in 2 Minutes [1 DIY Method / Only $3.89]

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