P28A5
Cylinder 6 Ion Current Sense Circuit Range/Performance
The ion current signal from cylinder 6 is outside the expected range for combustion conditions. Combustion quality cannot be assessed reliably.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Spark plug aged - electrode shape changedCommon
- Ion sense circuit gain driftPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- Spark Plug Cyl 6
- Ignition Coil Cyl 6
- Ion Sense Module
P28A5 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.