What it means
Ion current from cylinder 8 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 measures electrical activity through the cylinder 8 spark plug after ignition so the ECM can assess combustion. This code sets when the cylinder 8 sense signal rises above its expected window, which may be caused by coil-primary interference, a biased reference, or 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
- Engine misfire or rough running
- Reduced power
How to diagnose it
- Save freeze-frame data and compare live ion-current and misfire readings for cylinder 8 with other cylinders to identify when the high signal occurs.
- Inspect the cylinder 8 sense-wire routing near the ignition coil and look for damaged insulation or wiring positioned where coil-primary interference may couple into it.
- Check the cylinder 8 sense connector for corrosion, loose pins, or high-resistance contact.
- Inspect the cylinder 8 spark plug and coil connections for damage or tracking that could affect the signal.
- Test the cylinder 8 reference and signal circuits for bias, shorts, and unwanted coupling using the wiring diagram and manufacturer's specification.
Common fixes
- Clean and secure corroded or loose cylinder 8 sense connector terminals.
- Repair damaged cylinder 8 wiring and restore the specified separation and routing from ignition-coil wiring.
- Replace a damaged cylinder 8 spark plug or ignition component if inspection identifies a fault.
- Correct a biased reference or other confirmed sense-circuit fault.
Can I keep driving?
If the warning light is steady and the engine runs smoothly, limit driving and arrange diagnosis soon because an inaccurate cylinder 8 reading can hide combustion problems and emissions may rise. Stop if the engine misfires 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.