Code P0325, Knock Sensor Error: Notes

Knock sensor is used to detect engine detonation and allow PCM to retard Ignition Control (IC) timing based on signal being received. The circuitry within knock sensor causes PCM's supplied 5 volts signal to be pulled down, so that under a no knock condition circuit would measure approximately 2.5 volts. Knock sensor produces an AC signal which rides on the 2.5 volts DC voltage. Amplitude and signal frequency is dependent upon the 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 P0325 will set if either one of these conditions are present for 20 seconds.

Code P0325 will set when the following conditions are present.

• Voltage on signal circuit becomes greater than 3.5 volts or less than 1.5 volts.
• Either condition is present for 20 seconds.

With Code P0325 set, PCM will illuminate Malfunction Indicator Light (MIL) for remainder of the key cycle and retard spark timing (knock retard) by 10 degrees.

1. If Code P0325 is detected, PCM 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. PCM applies 5 volts through a pull-up resistor which should be present at knock sensor terminal.