P28B8Cylinder 11 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
- P28B8 is the general circuit code for ion sensing on cylinder 11: the evaluation electronics receive nothing usable from that cylinder, most often because the line from coil 11 is broken or its connector has lost contact. Eleven cylinders only occur on V12 and W12 engines, and none of them with ion sensing is publicly described; no manufacturer documents P28B8. The layout such a code presumes exists on Saab's Trionic T8, whose detection module has a dedicated ion input for every coil. Losing it leaves the engine computer blind to misfire and knock on that cylinder, and on T8, which has no camshaft sensor, ion pulses also serve to find the firing order. P0361 concerns the primary side of coil K, not the measuring path; P28B9 to P28BB cover the range and level faults.
- What you may notice
- MIL on with a circuit fault stored for cylinder 11
- Misfire and knock detection for cylinder 11 no longer available
- Cautious ignition timing with slightly reduced power
- Likely causes
- LikelyLoose, corroded or pushed-back pin in the cylinder 11 coil connector
- PossibleBroken ion signal wire between coil 11 and the evaluation module
- PossibleMeasuring stage inside coil 11 failed
- RareCylinder 11 input of the evaluation module damaged
- 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 – €750
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.