P234FCylinder 9 Pressure Variation Low
- 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
- P234F flags that the pressure signal of cylinder 9 changes too little: the rise and fall the ECM expects across each combustion cycle is missing or very small. For cylinder 9 there is no manufacturer documentation. In the Saab 9-5 with GM's 2.0 CDTI, the cylinder-1 analogue is P039C, labelled pressure variation too low, with three sub-faults; it reacts after more than 0.2 s out of range with the engine running and is grouped with the erratic code as a signal performance fault. Saab does not explain the exact measurement. A flat signal fits a sensing pin stuck in carbon that no longer passes on the pressure, a sensor that has lost sensitivity, or a cylinder that hardly builds up pressure. Usually only the warning lamp shows; the high counterpart is P2350.
- What you may notice
- Check engine light on
- Usually no change in engine behaviour
- Likely causes
- LikelySensing element of the glow plug stuck by carbon
- PossibleSensor lost sensitivity through ageing
- RareCylinder 9 builds up little pressure (compression or injection fault)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €100 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.