Knock Sensor 1 Circuit Input Intermittent (Bank 1 or Single Sensor)

Possible causes

• CommonFailed knock sensor
• CommonSensor loose, or tightened to the wrong torque - these only work when clamped correctly to the block
• CommonCorroded connector or damaged wiring
• PossibleGenuine engine noise the sensor is correctly hearing - worn bearings, a loose component, or detonation from poor fuel
• PossibleWiring routed against the engine, picking up interference
• RareFailed control module input

What you might notice

• Noticeably less power, especially under load or up hills
• Worse fuel economy
• Pinging or knocking under acceleration
• Check engine light on
• Often no symptom beyond the light

What to check, in order

1. Note whether it correlates with heat or with rough roads.
2. Wiggle-test the harness with the engine running.
3. Understand what has been lost. The module listens for knock and retards ignition timing when it hears it; without a trustworthy sensor it retards timing as a precaution, which is why the car feels flat rather than sounding wrong.
4. Check the sensor is tight and correctly torqued. These sensors read vibration through their mounting, so a loose one or one tightened wrongly reports nonsense while looking perfect.
5. Inspect the connector and wiring - the harness runs across a hot engine.
6. Try a tank of the fuel grade the manufacturer specifies. Genuine detonation from low-octane fuel makes a working sensor report knock, and that is not a fault.
7. Find out where the sensor is before committing. On many V engines it sits under the intake manifold, and the labour costs far more than the part.