P28BBCylinder 11 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
- P28BB is stored when the cylinder 11 ion signal remains above the highest value the measuring circuit can legitimately produce. Common reasons are a sense wire shorted to battery voltage or to another ignition circuit, an internal breakdown in coil 11 that couples spark energy into the measuring output, and a missing ground at the evaluator that lifts the whole reference. The nearest published logic is per bank on Saab's T7 V6: P1324 needs a combustion line above 5 V throughout 200 combustions and clears only after 300 clean ones; Saab handled it as a Type III fault without a warning lamp. A stuck-high reading looks like constant combustion and can hide genuine misfire. No manufacturer documents P28BB. Its low-side partner is P28BA; the module supply is checked by P28C0 to P28C2.
- What you may notice
- Stored code for a high ion signal on cylinder 11, lamp behaviour depends on the maker
- Real misfire on cylinder 11 may go undetected
- Retarded timing on cylinder 11
- Likely causes
- LikelyIon signal wire of cylinder 11 shorted to battery voltage or another ignition circuit
- PossibleInternal breakdown in coil 11 feeding spark energy into the signal
- RarePoor ground of the evaluation module shifting the reference
- 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 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.