What it means
The ECM cannot read a valid ion current signal from cylinder 9. Ion current sensing relies on the spark plug acting as an electrode after combustion.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The ion-current system uses the spark plug in cylinder 9 as an electrode after combustion, letting the ECM read a signal related to combustion. This code sets when the ECM cannot obtain a valid cylinder 9 ion-current signal, commonly because the ion-sense module or the cylinder 9 wiring and connector has a fault.
Common causes
Most likely first.
- Ion sense module failed
- Wiring or connector fault
Symptoms
- Check-engine light
- Engine misfire or rough running
- Reduced power
How to diagnose it
- Record freeze-frame data and review live misfire or ion-current information to confirm the problem is associated with cylinder 9 and identify its operating conditions.
- Inspect the cylinder 9 sense wiring and connector for looseness, corrosion, chafing, heat damage, or disconnection.
- Check the cylinder 9 spark plug and ignition connections for visible damage or contamination.
- Use the wiring diagram to test the cylinder 9 sense circuit for opens and shorts, following the manufacturer's specification.
- If circuit checks pass, test the ion-sense module and its cylinder 9 channel using the vehicle's specified procedure.
Common fixes
- Reconnect or clean and secure the cylinder 9 sense-circuit connector.
- Repair damaged, open, or shorted cylinder 9 sense wiring.
- Replace a cylinder 9 spark plug if inspection confirms it is fouled or damaged.
- Replace the ion-sense module if testing confirms its cylinder 9 channel has failed.
Can I keep driving?
With a steady warning light and smooth running, a short gentle drive may be possible, but the fault can impair misfire monitoring and increase emissions. Stop if the engine misfires severely or loses power, and avoid hard acceleration.
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.