P0263Powertrain
Powertrain · SAE
Cylinder 1 Contribution/Balance — Deviation
Meaning
The ECM has detected that cylinder 1 is delivering a significantly different fuel quantity compared to the other cylinders. The cylinder balance/contribution monitor has detected an imbalance exceeding the allowable tolerance threshold.
Common causes
- Worn, clogged, or flow-drifted injector on cylinder 1
- Low compression on cylinder 1 (valves, rings, head gasket)
- Fuel circuit restriction or leak at cylinder 1
- Faulty spark plug or ignition coil (gasoline engines)
- Common rail pressure sensor drift (diesel engines)
- Intake manifold leak at cylinder 1 port
Symptoms
- Malfunction indicator lamp (MIL) illuminated
- Sporadic misfire or torque imbalance at cylinder 1
- Vibrations at idle or under load
- Abnormal fuel consumption
- Possible exhaust smoke
Severity
Moderate: prolonged imbalance can lead to misfire, catalytic converter damage, and degraded engine performance.
What to do
- Perform injector balance/contribution test with a scan tool (cut-out test)
- Check cylinder 1 compression pressure
- Inspect and test cylinder 1 injector (flow rate, seal, spray pattern)
- Check spark plug and coil (gasoline) or common rail system (diesel)
- Replace injector if flow is out of specification