Circuit Description

The knock sensor (KS) system enables the powertrain control module (PCM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The PCM monitors two sensors. Each KS produces an AC signal that varies at 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 receives the KS signal through a signal circuit. The KS ground is supplied by the engine block through the sensor housing. The PCM uses the KS signal to calculate an average voltage range. The PCM inspects the KS and the related wiring by comparing the actual knock signal to the assigned voltage range. If the KS system is operating correctly, the PCM should monitor the KS voltage that is varying above and below the predetermined average voltage. If the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system, DTC P0325 sets.