GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Corvette 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC P0325

Circuit Description

The knock sensor (KS) system 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 ECM monitors two separate KS, one on each side of the engine block. Each KS produces an AC voltage signal that varies with different engine speeds and loads. 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 KS ground is supplied by the ECM through a low reference circuit. The ECM uses the KS signal to calculate the average voltage, then assign a voltage range value. The ECM will then monitor for a normal KS signal within the assigned voltage range. If the ECM malfunctions in a condition that will not allow proper diagnosis of the KS system, DTC P0325 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0325 Knock Sensor (KS) Circuit

Conditions for Running the DTC
    • The engine run time is more than 10 seconds.
    • The engine speed is greater than 500 RPM.
    • DTC P0325 runs continuously when the above conditions are met.

Conditions for Setting the DTC

The ECM detects a malfunction in the KS diagnostic circuitry that will not allow proper diagnosis of the KS system for 100 milliseconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC last test failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 3

Go to Intermittent Conditions

3

Replace the engine control module (ECM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 4

--

4
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 5

5

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK