GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Century 🢒 Restraints 🢒 SIR 🢒 DTC P0325

Circuit Description

The knock sensor (KS) produces an alternating current voltage at all engine speeds and loads. The powertrain control module (PCM) then adjusts the spark timing based on the amplitude and on the frequency of the KS signal. The PCM uses the KS signal in order to calculate the average voltage and assigns a voltage value. The PCM inspects the KS and the related wiring by comparing the actual knock signal to the assigned voltage range. A normal KS signal should remain out of the assigned voltage range. This DTC will set if the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0325 Knock Sensor (KS) Module Performance

Conditions for Running the DTC
    • DTCs P0016, P0101, P0102, P0103, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0335, P0336, P0340, P0341, P0502, or P0503 are not set.
    • The engine speed is between 1,000-5,000 RPM.
    • The throttle angle is more than 15 percent .
    • The engine load is more than 45 percent .
    • The engine coolant temperature (ECT) is more than 60°C (140°F).
    • The maximum spark retard is less than 15 degrees.
    • The system voltage is more than 9 volts.
    • The engine run time is more than 30 seconds.
    • The diagnostic runs continuously when the above conditions are met.

Conditions for Setting the DTC
    • The PCM detects a malfunction in the KS diagnostic circuitry which will not allow proper diagnosis of the KS circuit.
    • The above condition exists for at least 1 second.

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

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 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, or within the observed parameters of the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

Go to Step 3

Go to Intermittent Conditions

3

Replace the powertrain control module (PCM). 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