What it means
The ion current signal from cylinder 7 is outside the expected range for combustion conditions. Combustion quality cannot be assessed reliably.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
After ignition, the ECM reads ion current at cylinder 7's spark plug to assess combustion. This code sets when cylinder 7's signal is present but outside the expected range for the recorded operating conditions.
Common causes
Most likely first.
- Spark plug aged - electrode shape changed
- Ion sense circuit gain drift
- Sensor element aged beyond calibration window
Symptoms
- Check-engine light on
- Rough idle or engine misfire
- Reduced engine performance
How to diagnose it
- Use freeze-frame and live data to identify when cylinder 7's ion-current signal leaves range and whether other cylinders show a similar pattern.
- Inspect the cylinder 7 spark plug for an altered or eroded electrode, deposits, oil, or damage that could affect sensing.
- Check cylinder 7's ion-sense wiring and connector for corrosion, loose pins, heat damage, or routing near ignition-coil wiring.
- Compare cylinder 7's readings with other cylinders under similar conditions to determine whether the fault is local or shared.
- Test the cylinder 7 sense path, reference, and module gain against the manufacturer's specification before replacing the sensor or module.
Common fixes
- Replace an aged or damaged cylinder 7 spark plug with the specified type.
- Clean and secure corroded or loose cylinder 7 ion-sense connector contacts.
- Repair damaged or poorly routed cylinder 7 ion-sense wiring.
- Replace a faulty ion-sense element or module if tests confirm gain drift or sensor failure.
Can I keep driving?
If the engine runs smoothly, limit driving and avoid hard acceleration until diagnosed; unreliable cylinder 7 combustion monitoring can allow a misfire to go unnoticed and increase emissions. Stop driving if it misfires severely or loses power.
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.