P289CCylinder 4 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
- P289C stands for a general circuit fault in the ion measurement of cylinder 4, meaning no usable signal reaches the evaluation electronics from that plug. Cylinder 4 has a special role in Saab's Trionic four-cylinders: without a camshaft sensor, the engine fires cylinders 1 and 4 at the same time during start-up and decides from the ion response which of them is on the compression stroke. On the T8, coil 4 delivers its signal to processing module pin 15, and a combustion in cylinder 4 is passed on as a pulse to engine module pin 21(B). On a V6 with Saab's T7, cylinder 4 instead sits in bank 2 next to 2 and 6. Saab used in-house codes; no manufacturer publicly documents P289C.
- What you may notice
- MIL with ion fault stored for cylinder 4
- Extended cranking because cylinder 1 and 4 cannot be told apart reliably
- Conservative ignition timing with reduced power
- Likely causes
- LikelyIon measuring stage in the coil of cylinder 4 failed
- PossibleOpen circuit between coil 4 and the processing module
- RareCylinder 4 input of the processing module defective
- 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: €60 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.