What it means
The primary control circuit of ignition coil G reads a voltage below the expected level — usually a short to ground on the primary driver wire or a low-resistance fault in the coil primary winding. Coil G cannot build a normal charge, so the cylinder it fires misfires, especially under load. Causes: short to ground in the primary wiring, an internal coil primary fault, or a faulty ECU/igniter driver.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Coil G's primary control circuit carries the low-voltage current that charges the coil before it fires. The control module sets this code when it detects voltage below the expected level, often because the circuit is shorted to ground or the coil primary has a fault; the cylinder served by coil G may misfire.
Common causes
Most likely first.
- Primary winding shorted to ground or harness chafed
- Coil G internal driver fault
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Engine misfire or rough running
- Reduced power or hesitation
How to diagnose it
- Record freeze-frame data and check live misfire counts to see whether the coil G cylinder is affected.
- With the ignition off, inspect coil G's connector and harness for chafing, pin damage, corrosion, or wiring touching ground.
- Check that the coil G connector is seated and its terminals make clean, secure contact.
- Use the wiring diagram to test the coil G primary control circuit for a short to ground, comparing results with the manufacturer's specification.
- If the harness checks out, test coil G's primary winding and driver circuit using the manufacturer's procedure.
Common fixes
- Clean and secure corroded or loose coil G connector terminals.
- Repair chafed coil G wiring that is shorted to ground.
- Replace coil G if its primary winding fails testing.
- Repair the control driver only if circuit tests identify it as faulty.
Can I keep driving?
Limit driving and avoid heavy acceleration because the coil G cylinder may misfire under load. If the check-engine light flashes or the engine runs very roughly, stop when safe to reduce the risk of catalytic-converter damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.