P03D8Cylinder 7 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
- Some diesels have a combustion pressure sensor in the glow plug; the engine module uses it to control injection for each cylinder. This code concerns cylinder 7. P03D8 means the swing of the pressure signal is too small. The only manufacturer we found using this code family, GM's European 2.0 CDTI four-cylinder diesel (Saab 9-5, 2010), uses 'pressure variation too low' for cylinders 1 to 4: signal outside its range for more than 0.2 s with the engine running; what exactly is measured, Saab does not explain – presumably the signal barely responds, for example because a coked glow rod no longer transmits the pressure. For cylinder 7, which only engines with at least 7 cylinders have, no manufacturer document available to us uses the code; the description follows that logic and CARB. Usually there are no noticeable symptoms.
- What you may notice
- Check engine light on
- Usually no noticeable symptoms
- Possibly rough running or combustion noise because control is off
- Likely causes
- LikelyPressure-sensing glow plug faulty or coked (glow rod stuck)
- PossibleContact resistance in connector or ground
- RareActual compression loss or misfire in the cylinder
- 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 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.