What it means
Ion current from cylinder 7 is above the expected window. Cross-coupled signal, biased reference, or sensor fault.
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 7 to detect electrical activity in the gases after the spark, helping the ECM assess combustion. This code sets when the cylinder 7 sense circuit reports a signal above its expected window, which can result from ignition-coil interference, a biased reference, or a poor connector contact.
Common causes
Most likely first.
- Inductive cross-coupling from ignition coil primary
- Sense reference voltage biased
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light on
- Rough idle or engine misfire
- Reduced engine performance
How to diagnose it
- Record freeze-frame data and compare live misfire or ion-current data for cylinder 7 with other cylinders to see when the high reading occurs.
- Inspect the cylinder 7 ion-sense and ignition-coil wiring for routing damage, loose connections, or signs that the sense lead runs close to the coil primary wiring.
- Check the cylinder 7 connector and terminals for corrosion, looseness, or poor contact that could distort the signal.
- With the ignition off, inspect the cylinder 7 spark plug and coil connections for damage or tracking that could contribute to electrical interference.
- Use the vehicle wiring diagram to test the cylinder 7 sense reference and signal circuit for bias, shorts, or unwanted coupling, comparing results with the manufacturer's specification.
Common fixes
- Clean and secure corroded or loose cylinder 7 sense-circuit connector terminals.
- Repair damaged cylinder 7 sense or ignition-coil wiring and restore the specified wire routing.
- Replace a damaged cylinder 7 spark plug or ignition component if inspection identifies a fault.
- Repair a biased reference or cross-coupled cylinder 7 sense circuit after confirming the fault by circuit testing.
Can I keep driving?
If the engine runs smoothly and the warning light is steady, limit driving and arrange diagnosis soon because misfire can increase emissions and may damage the catalytic converter. Stop driving if it runs roughly or loses power, and avoid heavy 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.