GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0325: Knock Sensor (KS) Module Performance

Circuit/System Description

The knock sensor (KS) enables the engine control module (ECM) 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 voltage signal that varies depending on the vibration level during engine operation. The ECM adjusts the spark timing based on the amplitude and the frequency of the KS signal. The ECM receives the KS signal through a signal circuit . The ECM supples a ground circuit to the KS through a low reference circuit . The ECM also supplies a shielded ground circuit to the KS. The ECM learns a KS noise level at idle and uses calibrated values for the rest of the engine speed range. The ECM should monitor a normal KS signal within the noise channel.

Conditions for Running the DTC

    • DTCs P0106, P0107, and P0108 are not set.
    • The engine speed is more than 1600 RPM.
    • The engine coolant temperature (ECT) is more than 50°C (122°F).
    • The manifold absolute pressure (MAP) is between 10 kPa and 50 kPa which depends on engine speed.
    • DTC P0325 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The control module has detected an internal circuitry fault.

Action Taken When the DTC Sets

DTC P0325 is a Type C DTC.

Conditions for Clearing the DTC

DTC P0325 is a Type C DTC.

Reference Information

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Circuit/System Testing

Ignition ON, observe the DTC information with a scan tool.

If DTC P0325 failed this ignition, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine control module replacement, setup, and programming.