DTC P0325: Knock Sensor Module Circuit: Description
WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
The Knock Sensor (KS) produces an AC voltage at all engine speeds and loads. The Powertrain Control Module (PCM) then adjusts the spark timing based on the amplitude and frequency of the KS signal. The PCM uses the KS signal to calculate the average voltage range. The PCM checks the knock sensor and related wiring by comparing the actual knock signal to the calculated voltage range. If the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system DTC P0325 sets.