When Monitored and Set Condition:
WARNING: This page is about a different car, the 2004 Dodge Pickup and 2004 Dodge Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
When Monitored: With the ignition on and the engine running.
Set Condition: Knock Sensor #1 or #2 signal below minimum acceptable threshold voltage at particular engine speeds or above 5.0 volts.