GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 Envoy XUV 🢒 DTC 🢒 DTC P0325

Circuit Description

The knock sensors (KS) produce an AC signal under all engine operating conditions. The powertrain control module (PCM) calculates the average voltage range of each KS signal. If the KS system is operating normally, the PCM should monitor the KS voltage varying above and below a calculated average voltage. This DTC will set if the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system.

Conditions for Running the DTC
    • The engine run time is more than 10 seconds.
    • The ignition voltage is more than 10 volts.

Conditions for Setting the DTC
    • A malfunction with the KS system within the PCM are faulty.
    • All of the above conditions are present for 12 seconds.

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 the 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 malfunction indicator lamp (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 Controls Connector End Views or Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step  2

Go to Diagnostic System Check - Engine Controls

2

Important: If you can hear the engine knock, repair the engine mechanical problem before proceeding with this diagnostic.

  1. Observe the Freeze Frame/Failure Records data 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 as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed

Does the DTC fail this ignition?

Go to Step 3

Go to Intermittent Conditions

3

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step  4

--

4
  1. Use the scan tool in order to clear the DTCs
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the conditions for Running the DTC as specified in the supporting text.

Does the scan tool indicate that this test ran and passed?

Go to Step  5

Go to Step  2

5

Select the Capture Info option and the Review Info option using the scan tool.

Does the scan tool display any DTCs that you have not diagnosed?

Go to DTC List Diagnostic Trouble Code (DTC) List

System OK