What it means
The ECM cannot read a valid ion current signal from cylinder 8. 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 8 as an electrode after combustion, allowing the ECM to monitor the resulting signal. This code sets when the ECM cannot obtain a valid cylinder 8 ion-current reading, often because the ion-sense module or its wiring and connector has failed.
Common causes
Most likely first.
- Ion sense module failed
- Wiring or connector fault
Symptoms
- Check-engine light on
- Rough idle or engine misfire
- Reduced engine performance
How to diagnose it
- Save freeze-frame data and check live misfire and ion-current information to confirm the fault is associated with cylinder 8 and note the conditions when the signal disappears.
- Inspect the cylinder 8 ion-sense wiring and connector for disconnection, chafing, heat damage, corrosion, or loose terminals.
- Check the cylinder 8 spark plug and ignition connections for visible damage or contamination that could interrupt sensing.
- Use the wiring diagram to check continuity and shorts in the cylinder 8 sense circuit, following the manufacturer's specification.
- If the wiring and connections pass, test the ion-sense module and its inputs and outputs using the vehicle's specified procedure.
Common fixes
- Reconnect or clean and secure the cylinder 8 ion-sense connector.
- Repair an open, shorted, or damaged section of cylinder 8 sense wiring.
- Replace a faulty cylinder 8 spark plug if inspection shows it is damaged or fouled.
- Replace the ion-sense module if circuit checks confirm it has failed.
Can I keep driving?
A steady warning light with smooth running usually allows a short, gentle trip for diagnosis, but the fault can prevent reliable 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.