P2318
Ignition Coil G Primary Control Circuit Low
Ignition system
Generic OBD-II
High
What it means
P2318 means the ECM sees low voltage on the primary control circuit for ignition coil G — typically a short to ground in the control wire, a failed coil, or a bad connector. With the coil not firing correctly, the affected cylinder misfires, causing rough running and lost power. It's worth fixing promptly to avoid catalytic-converter damage.
High
Can I keep driving? Reduced — coil G likely isn't firing, so expect a misfire on that cylinder; avoid extended driving to protect the catalytic converter.
Common symptoms
What you'll notice
- Misfire on one cylinder
- Rough idle and shaking
- Hesitation and loss of power
- Check-engine light on (may flash during an active misfire)
- Poor fuel economy
Common causes
Most likely first
- Short to ground in the coil G primary control wire (reads low voltage)Likely
- Faulty ignition coil GCommon
- Corroded or damaged connector at the coilCommon
- ECM ignition driver faultLess often
How to diagnose & fix
Work through it in order
- Locate coil G for your engine and read freeze-frame data.
- Inspect the coil connector and primary control wiring for a short to ground or chafing.
- Measure the coil's primary-circuit resistance against spec.
- Swap coil G with a known-good coil to confirm the coil vs. the wiring.
- Repair the wiring or replace the coil, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2318?+
Only briefly. If coil G isn't firing, that cylinder misfires, and prolonged misfiring can damage the catalytic converter — keep driving to a minimum until it's fixed.
Can I just clear P2318?+
It returns as soon as the ECM sees the low-voltage control circuit again. The wiring short or coil fault has to be repaired.
Related codes
Often seen with P2318
Read & clear P2318 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX