P28A5Cylinder 6 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
- P28A5 points to a cylinder 6 ion signal that exists but makes no sense for the operating point: too little combustion response, a trace that jumps between cycles, or one that departs from the remaining cylinders. Since ionisation follows the actual burn, a misfiring or lean cylinder 6 can trigger it as readily as a worn plug or a wet plug well. On Saab's T7 V6 the bank 2 module evaluates the ion flow of cylinders 2, 4 and 6 for knock, sending the result to engine module pin 62, and missing combustion signals on cylinder 6 feed misfire code P0306. If the signal is unreliable, knock control tends to retard timing more often. No manufacturer publicly documents P28A5; P28A4, P28A6 and P28A7 are the electrical siblings.
- What you may notice
- MIL, often together with P0306
- Rough running at idle or light throttle
- Hesitation under acceleration
- Likely causes
- LikelySpark plug of cylinder 6 worn or sooted
- PossibleWater or oil in the plug well of cylinder 6
- PossiblePoor combustion in cylinder 6 (injector, valve, compression)
- 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 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.