P03B7Cylinder 4 Pressure Sensor Circuit Intermittent/Erratic
- 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 4. P03B7 means the sensor signal is erratic or drops out for moments. GM's European 2.0 CDTI diesel (Saab 9-5, 2010) calls it 'circuit erratic' and sets it when the signal is outside its range for more than 0.2 s with the engine running; its fault table groups the erratic and pressure variation codes together as signal performance faults. The test plan checks a reference of 4.8–5.2 V and a ground below 5 Ω before the glow plug is replaced. Typical causes are a loose contact at the glow plug connector, a chafed engine harness or sensor electronics that become unstable with temperature. The code often comes and goes; combustion control for the cylinder is suspended while it is active.
- What you may notice
- Check engine light on
- Occasionally rough running
- Often no symptoms, the code comes and goes
- Likely causes
- LikelyLoose contact at the glow plug connector
- PossibleChafing or broken wire in the engine harness
- PossibleSensor electronics of the glow plug unstable with temperature
- RareInterference from ground problems
- 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: €50 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.