P0351: Ignition Coil "A" Primary/Secondary Circuit Malfunction

written by Edmunds.com^{This story was created with generative AI and was reviewed and fact-checked by our staff of editors and experts.}
edited by Brett T. Evans^{Correspondent
Brett T. Evans has been an auto writer for more than a decade with 2,000 articles under his belt, covering topics as varied as tuned diesel trucks, modern supercars and experimental electric vehicles. Brett contributes to Edmunds and has also written for Petrolicious, MotorTrend, Out Motorsports and Motor1, among others. When he's away from his desk, Brett enjoys off-roading in his 1996 Lexus LX 450 or cutting up a twisty road in his 2006 BMW Z4 3.0si — sometimes with a border collie named Lilly in tow.}
4/10/2025
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What does the P0351 error code mean?

The P0351 diagnostic trouble code (DTC) stands for "Ignition Coil 'A' Primary/Secondary Circuit Malfunction." This code is triggered when the engine control module detects an issue with the ignition coil circuit on cylinder 1. The ignition coil is responsible for converting battery voltage into the high voltage needed to create a spark in the cylinder. A failure in this circuit can cause engine misfires and poor performance.

Why it's important to address the P0351 error code

A faulty ignition coil can lead to engine misfires, resulting in reduced power, rough idling and increased fuel consumption. If left unaddressed, prolonged misfires can damage the catalytic converter and other engine components. A malfunctioning ignition system can also make it difficult to start the vehicle and may cause unpredictable engine behavior, increasing the risk of a breakdown.

Can I safely drive my car with this error code?

Driving with the P0351 code is not advisable. A failing ignition coil can cause severe misfires that lead to power loss and hesitation, especially during acceleration. If misfires become frequent, unburned fuel can enter the exhaust system, potentially causing overheating and damage to the catalytic converter. You should address the issue immediately to prevent further mechanical issues.

Common symptoms of the P0351 error code

lluminated check engine light
Engine misfires or rough idling
Poor acceleration and reduced power
Increased fuel consumption
Difficulty starting the engine
Exhaust system overheating (in severe cases)

How is the P0351 error code diagnosed?

Diagnosing the P0351 code involves the following steps:

Use an OBD-II scanner: Confirm the presence of P0351 and check for additional misfire-related codes.
Inspect the ignition coil and wiring: Look for visible damage, loose connections or corrosion in the coil harness.
Test the ignition coil: Use a multimeter to check resistance levels in the primary and secondary circuits.
Swap coils: If applicable, swap the ignition coil with another cylinder’s coil and see if the misfire moves.
Check the engine control module: If the coil and wiring are functional, the engine control module may have a fault in controlling the ignition signal.

How is the P0351 error code repaired?

Repairs for the P0351 code may include:

Replacing the faulty ignition coil on cylinder 1.
Repairing or replacing damaged wiring and connectors.
Cleaning or replacing spark plugs if fouled due to misfires.
Inspecting and replacing the ignition control module if necessary.
Testing and replacing the engine control module if all other components are functioning properly.