Ignition Coil A Primary/Secondary Circuit Malfunction
There’s a problem with the ignition coil circuit for cylinder 1.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The ignition coil takes the battery's 12 volts and turns it into a high voltage (about 20,000-45,000 volts) needed to create a spark in the engine cylinder. If it’s malfunctioning, the engine may not start or run poorly.
What the computer is actually seeing
The engine control module (ECM) monitors the ignition coil's circuit for voltage and resistance. If it detects excessive resistance, no voltage, or a short circuit, it triggers the P0351 code.
What a healthy reading looks like
The expected resistance for the ignition coil is typically between 0.4 to 2.0 ohms for the primary side, and around 5,000 to 15,000 ohms for the secondary side. Voltage should be around 12 volts at the connector while cranking.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 1Check the battery voltage. It should be between 12.4 to 12.6 volts at rest. If low, charge the battery first.
- 2Inspect the wiring and connectors at the ignition coil for damage or corrosion. Repair as needed.
- 3Measure the resistance of the ignition coil using a multimeter. Check primary (should be 0.4-2.0 ohms) and secondary (should be 5,000-15,000 ohms) values. If out of range, replace coil.
- 4Check for proper voltage supply to the ignition coil connector during cranking. Voltage should be around 12 volts. If not, look for an open circuit.
- 5If all checks are okay but the code persists, consider testing the engine control module (ECM) for faults.
Common causes
- Faulty ignition coil
- Bad wiring or connectors
- Open circuit in the ignition coil circuit
- Faulty engine control module (ECM)
- Poor ground connection
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended as it can lead to misfires and further engine damage.
Will this code come back after clearing it?
Yes, if the underlying issue isn't fixed, the code will likely reappear.
What happens if I ignore this code?
Ignoring it can cause poor engine performance, increased emissions, and possible damage to the catalytic converter.
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