Cylinder 1 Contribution/Balance Fault
What does P0263 mean?
The P0263 code means the vehicle's onboard diagnostic system has detected: Cylinder 1 Contribution/Balance Fault. This is a moderate severity code.
Common Symptoms
- Engine misfire on cylinder 1
- Rough idle and vibration
- Check Engine Light illuminated
- Reduced engine power
- Engine runs unevenly at all speeds
Probable Causes (Ranked by Likelihood)
- Faulty cylinder 1 fuel injector (incorrect fuel delivery) Very High
- Low compression in cylinder 1 High
- Leaking or clogged injector on cylinder 1 High
- Intake manifold vacuum leak at cylinder 1 Moderate
- Worn camshaft lobe affecting cylinder 1 valve timing Low
Step-by-Step Diagnostic Procedure
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Perform a cylinder contribution test using a scan tool to compare power output of each cylinder
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Run a compression test on all cylinders -- cylinder 1 should be within 10% of the highest reading
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Perform an injector flow test or swap cylinder 1 injector with another cylinder to isolate the fault
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Check for vacuum leaks around cylinder 1 intake runner using carburetor cleaner or smoke machine
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If compression is low, perform a leak-down test to determine if valves, rings, or head gasket are the cause
Frequently Asked Questions
Can I drive with code P0263?
You can drive short distances. This code indicates cylinder 1 is not contributing its fair share of power, meaning the engine is running unbalanced. Avoid heavy loads or long trips.
Is P0263 common on diesel engines?
Yes. Cylinder contribution codes are more commonly seen on diesel engines where the PCM can precisely measure each cylinder's contribution to crankshaft acceleration.
What is a cylinder contribution test?
The PCM monitors crankshaft acceleration during each cylinder's power stroke. If one cylinder contributes significantly less than the others, it flags a contribution fault for that cylinder.