P289ECylinder 4 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
- P289E means the ion signal of cylinder 4 remains below the range the module expects. A ground fault on the line from coil 4, a plug whose insulator conducts the bias voltage away, or a coil that has stopped generating that voltage are the main suspects. In Saab's T7 four-cylinder cassette, cylinders 3 and 4 share one detector that pulses engine module pin 6; Saab notes that a short to ground on such a combustion line produced only misfire codes, while an open line was flagged as P1334. A dedicated low code for cylinder 4 separates this case. Since cylinder 4 is also the start partner of cylinder 1, a dead signal can affect synchronisation. The opposite reading is P289F.
- What you may notice
- MIL with low ion signal on cylinder 4
- Possible start delay or misfire codes
- Power reduced by safety timing on cylinder 4
- Likely causes
- LikelyIon signal line of cylinder 4 shorted to ground
- PossibleSpark plug insulator of cylinder 4 leaking the bias voltage
- PossibleBias voltage generation inside coil 4 failed
- 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 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.