P28B3Cylinder 9 Ion Current Sense Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P28B3 shows that the cylinder 9 ion signal is held above the range a working circuit produces. Shorts from the sense line to a powered conductor, a coil 9 leaking high-voltage energy into its measuring output, or water in the connector can push it there. The fault matters for emissions monitoring, because a signal that always reports strong combustion would let real misfire on cylinder 9 go unnoticed. As an analogue, Saab's V6 bank codes needed 300 clean combustions before reporting the circuit OK again, after a sustained over-voltage had set them. No manufacturer documents P28B3, and no ion-sensing engine with nine or more cylinders is publicly known. P28B2 is the low fault, P28B0 the open circuit.
- What you may notice
- MIL with high ion reading on cylinder 9
- Real misfire on cylinder 9 can go unnoticed
- Timing on cylinder 9 retarded as a precaution
- Likely causes
- LikelyCylinder 9 sense line shorted to a powered conductor
- PossibleCoil 9 leaking high-voltage energy into its measuring output
- RareWater in the coil 9 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: €40 – €650
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.