Ignition Coil F Primary/Secondary Circuit Malfunction
There’s an issue in the ignition coil F circuit that affects engine performance.
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 is not firing properly. It powers up and sends voltage to the spark plug, usually around 12V or more, at the right time. If it fails, the engine might misfire or not start at all.
What the computer is actually seeing
The engine control module (ECM) monitors the ignition coil's primary and secondary circuits. If it detects a voltage or resistance outside normal ranges when the engine is running, it triggers this code.
What a healthy reading looks like
Primary circuit voltage should be around 12V when the ignition is on; secondary circuit resistance should be between 0.5 - 1.5 ohms for the coil itself.
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.
- 11. Check the ignition coil F connector and wiring for damage or corrosion. Repair as necessary. Decision: If any damage is found, fix it and retest. If not, proceed.
- 22. Measure the primary circuit voltage at the coil with the ignition on, engine off. Should be around 12V. Decision: If voltage is not correct, investigate power supply to the ignition coils. If correct, proceed.
- 33. Test the resistance of the ignition coil F. It should be between 0.5 - 1.5 ohms. Decision: If resistance is out of range, replace the ignition coil. If in range, proceed.
- 44. Inspect spark plugs and their wiring. Replace if worn or damaged. Decision: If they are bad, replace and retest. If not, proceed to ECM.
- 55. If all previous components are good, test the ECM with a scan tool for additional codes or malfunctions.
Common causes
- Faulty ignition coil F
- Wiring issues between the coil and ECM
- Defective ECM
- Bad spark plugs or wires
- Corrosion in connectors
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not safe to drive if you're experiencing misfires; this can lead to engine damage or stalling.
Will this code come back after clearing?
If the underlying issue isn't fixed, yes, the code will come back.
Why does this code pair with P0350?
P0350 indicates a general ignition coil problem, while P0356 is specific to coil F, so both can appear together due to system-wide issues.
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