P0263
Cylinder 1 Contribution/Balance Fault
The ECU compares each cylinder's contribution to crankshaft speed (rough run analysis) and determined cylinder 1 contributes less or more than the average. This points to a mechanical or fuel delivery problem rather than a pure ignition fault.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Common causes
Ordered by how often each turns out to be the cause.
- Injector clogged or wornCommon
- Low compression on cylinderPossible
- Localized intake leakLess likely
Parts involved
- Fuel Injector
- Cylinder Compression
- Intake Valve
P0263 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.