Cylinder 2 Contribution/Balance Fault
The P0266 code means the vehicle's onboard diagnostic system has detected: Cylinder 2 Contribution/Balance Fault. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $150 - $1,200 (parts and labor)
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Common Symptoms
- Engine misfire on cylinder 2
- Rough idle and vibration
- Check Engine Light illuminated
- Uneven power delivery
- Engine shakes at idle
Probable Causes (Ranked by Likelihood)
- Faulty cylinder 2 fuel injector (incorrect fuel delivery) Very High
- Low compression in cylinder 2 High
- Leaking or clogged injector on cylinder 2 High
- Intake manifold vacuum leak at cylinder 2 Moderate
- Worn camshaft lobe affecting cylinder 2 valve timing Low
Step-by-Step Diagnostic Procedure
-
Perform a cylinder contribution test using a scan tool to compare each cylinder's power output
-
Run a compression test -- cylinder 2 should be within 10% of the highest reading
-
Swap cylinder 2 injector with another cylinder to isolate whether the injector is at fault
-
Use a smoke machine to check for vacuum leaks around cylinder 2 intake port
-
If compression is low, perform a leak-down test to pinpoint valves, rings, or head gasket
Frequently Asked Questions
Can I drive with code P0266?
You can drive short distances. The engine is running unbalanced with cylinder 2 contributing less power. Avoid towing or heavy loads until repaired.
Why do diesel engines get contribution codes more often?
Diesel engine PCMs use crankshaft acceleration monitoring to precisely measure each cylinder's power contribution. This allows them to detect imbalances that gasoline engines typically flag as misfire codes instead.
Can a clogged injector cause a contribution fault?
Yes. A partially clogged injector delivers less fuel than commanded, resulting in reduced power output from that cylinder, which the PCM detects as a contribution fault.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0266 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
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