GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Century 🢒 DTC 🢒 DTC P0325 Knock Sensor Module Performance

Object Number: 387914 Size: SF
Engine Controls Components
Cell 20: Ignition System and Knock Sensor
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM contains integrated Knock Sensor (KS) diagnostic circuitry. An input signal from the knock sensor is used to detect engine detonation, allowing the PCM to retard Ignition Control (IC) spark timing based on the amplitude and frequency of the KS signal being received. The knock sensors produce an AC signal under all engine operating conditions. During engine operation, the PCM calculates the average voltage of the knock sensor signal. If the PCM malfunctions in a manner which will not allow proper diagnosis of the KS circuit, DTC P0325 will set.

Conditions for Running the DTC
    •  No TP, MAF, ECT, CKP, CMP sensor, VSS, DTCs are set.
    •  Engine speed is between 1000 and 5000 RPM.
    • The engine has been running for a minimum of 30 seconds.
    •  Throttle angle is greater than 15%.
    •  Engine load is greater than 45%.
    •  Engine coolant temperature is greater than 60°C (140°F).
    •  Maximum spark retard is less than 15 degrees.
    •  System voltage is greater than 9 volts.

Conditions for Setting the DTC
    •  The PCM detects a malfunction in the integrated knock sensor diagnostic circuitry which will not allow proper diagnosis of the knock sensor circuits.
    •  Above conditions for at least 30 seconds.

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

Conditions for Clearing the MIL/DTC
    • The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed.
    • The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using a scan tool.

Diagnostic Aids

Check for the following conditions:

Important: :  Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

    •  Poor terminal connection.
         Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Intermittents and Poor Connections Diagnosis , and Connector Repairs Wiring Systems.
    •  Damaged harness.
         Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems.
    •  Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

  1. Ensures that the malfunction is present.

    2.

  2. If sent here from symptoms, proceed with the diagnostic table.

    3.

  3. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain OBD System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Important: :  If a mechanical engine knock can be heard repair the engine mechanical problem before proceeding with this diagnostic. Refer to Base Engine Misfire Diagnosis .

  1. Operate engine within conditions specified in diagnostic support. Refer to Conditions for Setting the DTC.
  2. Using a scan tool, monitor Specific DTC info for DTC P0325 until the DTC P0325 test runs.

Note test result, does scan tool indicate DTC P0325 failed this ignition?

--

Go to Step 4

Go to Step 3

3

  1. Turn on the ignition switch.
  2. Review and record scan tool Fail Records data for DTC P0325.
  3. Operate vehicle within Fail Records conditions.
  4. Using a scan tool, monitor Specific DTC info for DTC P0325 until the DTC P0325 test runs.

Does scan tool indicate DTC P0325 test failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

Important: :  The replacement PCM must be programmed.

Replace the PCM.Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 5

--

5
  1. Review and record Fail Records data.
  2. Clear DTCs.
  3. Operate the vehicle within Fail Records conditions.
  4. Using a scan tool, monitor Specific DTC info for DTC P0325 until the DTC P0325 test runs.

Does the scan tool indicate DTC P0325 test failed this ignition?

--

Go to Step 2

System OK