Knock Sensor Description
WARNING: This page is about a different car, the 2005 Suzuki Reno and 2005 Suzuki Forenza. However, it is still accessible from the selected car via links, so may be relevant.
The knock sensor detects abnormal knocking in the engine. The sensor is mounted in the engine block near the cylinders. The sensor produces an AC output voltage which increases with the severity of the knock. This signal is sent to the engine control module (ECM). The ECM then adjusts the ignition timing to reduce the spark knock.