P2899Cylinder 3 Ion Current Sense Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- With P2899 an ion signal from cylinder 3 does arrive, yet it fails the plausibility check: its amplitude is too weak for the current load, it fluctuates without reason, or it no longer matches the pattern of the remaining cylinders. Because the measurement mirrors how hot and how highly compressed the burning charge is, an actual combustion weakness in cylinder 3 can be the cause just as much as a degraded plug with a leakage path. In Saab's 2009 detection module, cylinder 3 enters on its own input and is merged with cylinder 1 into the first combustion signal, while a band-pass branch extracts knock ringing from the same raw trace. No maker documents P2899 publicly. Hard electrical faults on cylinder 3 are P2898, P289A and P289B.
- What you may notice
- MIL, possibly together with P0303
- Slight roughness at idle or under light load
- Knock control retards timing more than usual
- Likely causes
- LikelySpark plug of cylinder 3 with deposits or excessive gap wear
- PossibleWeak combustion in cylinder 3 (lean injector, low compression)
- RareDamaged plug boot or moisture at the coil 3 connection
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.