DTC P0325: Knock Sensor Module Circuit: Description
WARNING: This page is about a different car, the 2002 Cadillac Seville, 2002 Cadillac Eldorado, and 2002 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) uses a knock sensor (KS) in order to detect the engine detonation (spark knock). The KS produces an AC signal during all engine speeds and loads. The PCM makes adjustments to the spark timing based on the amplitude and frequency of the KS signal. The PCM uses the KS in order to calculate the amount of normal engine noise (a noise channel) for a wide range of engine speeds and loads. The PCM compares the actual KS signal to the learned noise channel. If the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system, this DTC will set.