Cylinder 9 Pressure Too Low
Cylinder 9 measured peak combustion pressure is below the calibrated minimum — typically low compression, weak injection, or stuck-open exhaust valve.
Affected components
- Cylinder 9 combustion
- Cylinder compression
- Fuel injector cyl 9
Common causes
- High likelihood: Low compression on cylinder 9 (valves, rings, head gasket)
- Medium likelihood: Injector flow too low
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.