P28AA
Cylinder 7 Ion Current Sense Circuit Low
Ion current from cylinder 7 is below the expected window. Spark plug fouled, signal wire shorted to ground, or sensing path interrupted.
- 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 fouled with carbon or oilCommon
- Sense wire shorted to groundPossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Spark Plug Cyl 7
- Ignition Coil Cyl 7
- Ion Sense Module
P28AA 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.