P2320
Ignition Coil "G" Secondary Circuit
- Severity
- High
- Driving
- Short journeys only
A fault on the secondary - high voltage - side of ignition coil "G". The secondary is everything after the coil steps the voltage up: the coil's secondary winding, the boot, the spark plug and the gap the spark has to jump. The module cannot measure tens of thousands of volts directly, so it infers a problem from how the primary behaves as the spark fires. That means a worn plug or a cracked boot sets a coil code even when the coil itself is in good order, and this code is more often a plug problem than a coil problem. The coil letter is the manufacturer's designation and does not necessarily correspond to the cylinder number - the vehicle's own documentation says which is which, and a misfire code stored alongside will usually name the cylinder directly.
Possible causes
- CommonWorn spark plug, or one gapped wider than specification
- CommonSpark plug well past its service interval
- CommonCracked coil boot, or carbon tracking down the outside of it
- CommonOil in the plug well from a leaking cam cover gasket, letting the spark track to earth
- CommonFailed coil with a breakdown in the secondary winding
- PossibleWrong heat range or wrong type of plug fitted
- PossibleWater sitting in the plug wells after washing the engine
What you might notice
- Misfire - the engine shaking, especially at idle
- Loss of power and hesitation
- Check engine light on, or flashing
- Poor fuel economy
- Smell of unburnt fuel from the exhaust
What to check, in order
- Pull the spark plug for that cylinder and look at it before touching the coil. A worn or wrongly gapped plug is the most common cause of this code, and it is the cheapest thing on the list.
- Check the plug well for oil. A leaking cam cover gasket fills the well and the spark tracks to earth through the oil rather than jumping the plug gap - replacing the coil without fixing the leak just ruins the new one.
- Inspect the boot for cracks and for carbon tracking, which shows as a thin dark line running down the outside.
- Compare the plug gap against specification rather than assuming. Gaps open up as the electrode wears, and the coil has to produce more voltage to bridge them until it cannot.
- Swap the suspect coil with one from a neighbouring cylinder and see whether the fault follows it. This is the single most effective test available and it costs nothing - but only do it on engines where the coils are genuinely interchangeable.
- Do not fit a new coil onto a worn plug. The plug is what made the coil work hard enough to fail, and the new coil will go the same way.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.