What Does P0266 Mean?
The ECM has detected a contribution or balance fault on cylinder 2, meaning this cylinder is not producing its expected share of engine torque. The crankshaft speed variation analysis shows cylinder 2 is underperforming relative to the other cylinders, indicating a mechanical, fuel delivery, or ignition problem specific to that cylinder.
Common Causes
30%
Faulty cylinder 2 fuel injector with degraded spray pattern or flow rate
30%
Low compression on cylinder 2 from worn rings, leaking valve, or head gasket breach
25%
Cylinder 2 glow plug or ignition component failure causing incomplete combustion
15%
Restricted intake or exhaust for cylinder 2
Diagnostic Steps
1
Step 1: Run a cylinder power balance test by individually disabling injectors — cylinder 2 should show measurable RPM drop when disabled. Minimal drop confirms it is already not contributing.
2
Step 2: Perform a compression test on cylinder 2 and compare to adjacent cylinders — variation greater than 10% indicates mechanical issue.
3
Step 3: Perform a leak-down test on cylinder 2 — greater than 15% leakage indicates valve, ring, or gasket issues. Listen for leak location.
4
Step 4: Swap cylinder 2 injector with an adjacent cylinder and retest contribution balance.
5
Step 5: For gas engines, swap ignition coil from cylinder 2 with an adjacent cylinder and monitor for fault migration.
Estimated Repair Cost
$150 - $2,000
Parts + labor, varies by vehicle and location
The ECM has detected a contribution or balance fault on cylinder 2, meaning this cylinder is not producing its expected share of engine torque. The crankshaft speed variation analysis shows cylinder 2 is underperforming relative to the other cylinders, indicating a mechanical, fuel delivery, or igni...
The most common cause of P0266 (Cylinder 2 Contribution/Balance Fault) is: Faulty cylinder 2 fuel injector with degraded spray pattern or flow rate
Typical repair costs for P0266 range from $150 to $2,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Engine runs rough with reduced power. Drivable but diagnose promptly to prevent worsening mechanical damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0266 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Mechanical / Fuel Injection System
Difficulty
Type
Generic (SAE)
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