Knock Sensor System Operation

Normal Knock Sensor Signal:

Abnormal Knock Sensor Signal:

Knock Sensor System Operation

The PCM contains integrated Knock Sensor (KS) Diagnostic Circuitry. Input signals from the knock sensors are used to detect engine detonation, allowing the PCM to retard Ignition Control (IC) spark timing based on the amplitude and frequency of the KS signal being received. The knock sensors produce an AC signal under all engine operating conditions. The PCM calculates an average voltage of each knock sensor's signal and takes instantaneous signal voltage readings. The PCM uses the instantaneous signal voltage readings to determine the state of the knock sensor circuitry. If the knock sensor system is operating normally, the PCM should monitor instantaneous KS signal voltage readings varying outside a voltage range above and below the calculated average voltage(as shown in the normal knock sensor figure). If the PCM detects a knock sensor signal voltage within the calculated average voltage range, DTC P0327 or P0332 will set (as shown in the abnormal knock sensor figure).

If the PCM malfunctions in a manner which will not allow proper diagnosis of the knock sensor system, DTC P0325 will set.

DTCs P0327 and P0332 are designed to diagnose the knock sensors, and related wiring. Problems encountered with the KS system should set a DTC. However, if the customer's complaint is detonation/spark knock, use the tables for DTC P0327 or P0332 to diagnose the condition.