Cylinder 9 Above Knock/Combustion Vibration Sensor Threshold
The knock or combustion-vibration sensor monitors the structure-borne noise of each cylinder. The signal level for cylinder 9 has stayed above the diagnostic threshold for an extended period, indicating either persistent knock or an electrical fault that biases the channel high.
Affected components
- Knock sensor
- Knock sensor wiring
- Fuel octane quality
- Cylinder 9 combustion
Common causes
- High likelihood: Persistent knocking on cylinder 9 (low-octane fuel, carbon deposits, hot spot)
- Medium likelihood: Sensor or wiring biased high by short or moisture
- Low likelihood: Mechanical knock from bearings, piston pin or wrong torque
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.