P03B2Cylinder 3 Combustion Performance
- 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 3. P03B2 means the combustion quality in the cylinder, evaluated from the combustion pressure, is abnormal. No manufacturer document available to us describes the code; a GM patent shows the method: the ratio of measured to motoring pressure is turned into a measure of combustion energy, an inequality index against the neighbouring cylinders in firing order is formed, and a two-sided threshold detects partial combustion, misfire, injector and compression faults. CARB requires engines with a combustion or combustion quality sensor to detect misfire more sharply (5 % in 1,000 revolutions). Typical causes are a coked or leaking injector, compression loss or poor fuel; the engine runs roughly and smokes more.
- What you may notice
- Check engine light on
- Rough running, vibration
- Loss of power, more smoke and consumption
- Likely causes
- LikelyInjector coked, leaking or delivering the wrong quantity
- PossibleCompression loss (valve, rings)
- PossiblePartial combustion or misfire (fuel quality, EGR distribution)
- RarePressure sensor drifting
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.