P28ADCylinder 8 Ion Current Sense Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P28AD means the cylinder 8 ion signal is electrically intact but does not fit what the computer expects for the operating point, or it deviates clearly from the other cylinders. CARB treats such rationality checks as part of the monitoring of input components next to tests for wiring faults and for values outside the valid band. The current through the gap rises with pressure and temperature of the burning charge, so weak combustion from a worn plug, a partly blocked injector or poor compression in cylinder 8 lowers it, while oil deposits can distort it. On Saab's T8 the engine computer evaluates each cylinder only inside a crank-angle window after the spark. No manufacturer publicly documents P28AD. Circuit faults are P28AC, P28AE and P28AF; a confirmed misfire adds P0308.
- What you may notice
- MIL, often together with P0308
- Rough running under load
- Knock control intervenes more often on cylinder 8
- Likely causes
- LikelyWorn electrodes or wrong gap on the cylinder 8 plug
- PossiblePartly blocked injector on cylinder 8
- PossibleOil deposits on the cylinder 8 plug
- RareLow compression in cylinder 8
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €550
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.