What it means
Ion current from cylinder 12 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 engine control module uses ion current measured through the spark plug after ignition to assess combustion in cylinder 12. This code sets when cylinder 12's reported ion-current signal is higher than the expected range, which can result from ignition-coil interference, a biased sense reference, or a poor connection.
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
- Check freeze-frame data and cylinder-specific misfire or ion-current readings to see when cylinder 12's signal went high.
- Inspect cylinder 12's ion-sense and ignition-coil connectors and wiring for corrosion, loose pins, damage, or routing that could allow coil interference.
- Check the cylinder 12 connector terminals for corrosion or weak contact, since added contact resistance can distort the sense signal.
- Compare the ion-sense reference and cylinder 12 signal with the manufacturer's specifications while monitoring for a biased reference or an unusually high reading.
- If wiring and reference checks pass, test the cylinder 12 ignition coil and ion-sense components using the manufacturer's diagnostic procedure.
Common fixes
- Clean and secure corroded or loose cylinder 12 ion-sense connector terminals.
- Repair damaged or poorly routed cylinder 12 sense wiring that is exposed to ignition-coil interference.
- Repair a biased ion-sense reference circuit.
- Replace a confirmed faulty cylinder 12 ignition coil or ion-sense component.
Can I keep driving?
If the engine runs smoothly, limit driving and arrange diagnosis soon. If it misfires, runs rough, or loses power, avoid hard acceleration and stop driving if the symptoms become severe; continued misfiring can damage the catalytic converter.
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.