DTC P0325: Knock Sensor Module Circuit: Description
WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
The Knock Sensors (KS) produce an AC signal under all engine operating conditions. The Powertrain Control Module (PCM) calculates the average voltage range of each KS signal. If the KS system is operating normally, the PCM should monitor the KS voltage varying above and below a calculated average voltage. This DTC will set if the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system.