P28B4Cylinder 10 Ion Current Sense Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P28B4 is the basic circuit code for the ion current measurement of cylinder 10; typically the line from coil 10 to the evaluation module is interrupted or the coil's measuring stage is dead. Ten cylinders mean a V10 at minimum, where this is the last cylinder in the numbering, or a V12 or W12, where it is not. No production engine of that size with ion sensing is publicly described, and no manufacturer documents P28B4. Saab's systems illustrate the stakes: without the ion signal, misfire counting and cylinder-selective knock control lose their input, and the T7 V6 even cut fuel to every cylinder once a single discharge module lost its supply. Start at coil 10, plug and connector; P28B5, P28B6 and P28B7 are the range and level faults.
- What you may notice
- MIL with ion circuit fault for cylinder 10
- Cylinder 10 excluded from misfire and knock evaluation
- Possible power reduction through protective timing
- Likely causes
- LikelyOpen line between coil 10 and the evaluation module
- PossibleMeasuring stage of coil 10 dead
- PossibleCorroded terminals at the coil 10 connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €50 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.