Code P0325, Knock Sensor Error: Notes

Knock sensor is used to detect engine detonation and allow control module to retard Ignition Control (IC) timing based on signal being received. Circuitry within knock sensor causes control module's supplied 5 volts signal to be pulled down, so that under a no knock condition circuit would measure about 2.5 volts. Knock sensor produces an AC signal which rides on 2.5 volts DC voltage. Amplitude and signal frequency is dependent upon knock level.

If circuit becomes open or shorted to ground, voltage will either become greater than 3.5 volts or less than 1.5 volts. Code will set if either one of these conditions are present for 20 seconds. With code set, control module will illuminate Malfunction Indicator Light (MIL) for remainder of key cycle and retard spark timing (knock retard) by 10 degrees.

1. If code is detected, control module will retard spark timing by 10 degrees. If an audible is heard from engine, repair internal engine problem. Normally no knock should be detected at idle.
2. Control module applies 5 volts through a pull-up resistor which should be present at knock sensor terminal.