P0327 - Knock Sensor 1 Circuit Low Input (Bank 1)

P0327 is set when the Engine Control Unit (ECU) detects a voltage signal from the knock sensor (KS) that is below the operational threshold (typically less than 0.5V). The knock sensor is a piezoelectric sensor that converts mechanical vibrations into an AC voltage signal. Since the ECU monitors the reference voltage or bias voltage in the circuit, a 'low input' condition usually indicates a short to ground or an open circuit, preventing the ECU from monitoring engine detonation. As a fail-safe, the ECU will retard ignition timing to prevent engine damage.