DTC P0326: Knock Sensor Circuit Excessive Spark Retard: Description

WARNING: This page is about a different car, the 2003 Cadillac Seville and 2003 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.

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 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 PCM through a low reference circuit. The PCM uses the KS 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. When the PCM detects a KS signal that varies outside of the noise channel, the PCM will retard the spark timing until the knock goes away. If the knock is such that the vehicle operates on large amounts of spark retard and the PCM is unable to eliminate the knock, this DTC sets.