OBD-II code · Powertrain (generic, extended)
P28B9 Cylinder 11 Ion Current Sense Circuit Range/Performance
The ion current signal from cylinder 11 is outside the expected range for combustion conditions. Combustion quality cannot be assessed reliably.
Is it safe to drive with P28B9?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySpark plug aged - electrode shape changed
- PossibleIon sense circuit gain drift
- Less likelySensor element aged beyond calibration window
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.5–3 h
- Emissions test
- Likely to fail
- Parts involved
- Spark Plug Cyl 11, Ignition Coil Cyl 11, Ion Sense Module
Related codes
- P2891Cylinder 1 Ion Current Sense Circuit Range/Performance
- P2895Cylinder 2 Ion Current Sense Circuit Range/Performance
- P2899Cylinder 3 Ion Current Sense Circuit Range/Performance
- P289DCylinder 4 Ion Current Sense Circuit Range/Performance
- P28A1Cylinder 5 Ion Current Sense Circuit Range/Performance
- P28A5Cylinder 6 Ion Current Sense Circuit Range/Performance
- P28A9Cylinder 7 Ion Current Sense Circuit Range/Performance
- P28ADCylinder 8 Ion Current Sense Circuit Range/Performance
- P28B1Cylinder 9 Ion Current Sense Circuit Range/Performance
- P28B5Cylinder 10 Ion Current Sense Circuit Range/Performance
- P28BDCylinder 12 Ion Current Sense Circuit Range/Performance
- P28B6Cylinder 10 Ion Current Sense Circuit Low
- P28B7Cylinder 10 Ion Current Sense Circuit High
- P28B8Cylinder 11 Ion Current Sense Circuit
- P28BACylinder 11 Ion Current Sense Circuit Low
- P28BBCylinder 11 Ion Current Sense Circuit High
- P28BCCylinder 12 Ion Current Sense Circuit
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.