P2318: Ignition Coil G Primary Control Circuit Low
Do not keep driving
Stop if the engine light is flashing. Ask which cylinder this actually is on your engine before any dismantling starts — V8 cylinder numbering varies between manufacturers, coil G is frequently not cylinder 7, and reaching the wrong one can mean removing the intake manifold for nothing.
What this code means
Coil G's primary control circuit reads below its valid range. The primary and secondary distinction is at P2300, the spark plug argument at P2302, and the shared-supply caution at P2312.
A seventh coil means an eight-cylinder engine or larger, and that is where the lettering trap set out at P2303 does the most damage. Cylinder numbering on a V8 is not standardised at all: some manufacturers number straight down one bank and then the other, some alternate between banks in firing order, and the coil letters follow whichever scheme the manufacturer chose. Coil G is not cylinder 7 on many engines.
The cost of getting it wrong is higher here than on a four-cylinder, because reaching a coil on the inboard side of a V8 often means removing an intake manifold or a supercharger. Check the firing order and the manufacturer's cylinder numbering before anything is dismantled — it is a minute of looking against an afternoon of work on the wrong cylinder.
Likely causes
Start here
- Faulty ignition coil · easy
- Wiring shorted to ground · moderate
- Damaged wiring harness · moderate
Less common
- Faulty ignition coil driver in the module · specialist
- Corroded or loose connector · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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