P28A6Cylinder 6 Ion Current Sense Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P28A6 describes an ion reading from cylinder 6 that never leaves the bottom of its range. Between sparks the system keeps a small voltage across the plug, and the hot gas of a normal combustion lets a measurable current pass; if that voltage leaks to ground through a damaged conductor, a cracked ceramic or carbon deposits, or the coil stops supplying it, the reading collapses. With no usable value, the module treats cylinder 6 as unmonitored and usually falls back to safe timing. When tracing the fault, the harness along the cam cover deserves a close look for heat damage and chafed spots. No manufacturer documents P28A6 publicly; P28A7 is the high-side code.
- What you may notice
- MIL with low ion signal on cylinder 6
- Misfires on cylinder 6 possibly unrecorded
- Engine noticeably weaker on safe timing
- Likely causes
- LikelyDamaged ion conductor of cylinder 6 leaking to ground
- PossibleCracked ceramic or heavy deposits on the cylinder 6 plug
- PossibleCoil 6 no longer supplies the measuring voltage
- 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: €30 – €550
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.