P28B7Cylinder 10 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
- P28B7 means the ion signal of cylinder 10 is stuck above its valid window. The usual suspects are a sense lead shorted to a supply or to a neighbouring ignition circuit, breakdown inside coil 10 that lets spark energy into the measuring path, and a poor ground at the evaluation side that shifts the reference upward. A falsely high signal could pass as continuous combustion or as permanent knock, so the engine computer typically discards it and retards timing on that cylinder for safety. Saab's later T8 module, which processes the ion signal of each coil on its own input pin, shows the cylinder-selective layout such a code assumes. No manufacturer documents P28B7 publicly. The low-side fault is P28B6, module supply problems are P28C0 to P28C2.
- What you may notice
- MIL with high ion reading on cylinder 10
- Timing on cylinder 10 retarded for safety
- Misfire on cylinder 10 may be masked
- Likely causes
- LikelyCylinder 10 sense lead shorted to a supply or adjacent ignition circuit
- PossibleInternal breakdown in coil 10
- RarePoor ground at the evaluation side
- 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.