GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L (L43) 🢒 DTC P0325

Circuit Description

The knock sensor (KS) produces an AC voltage at all engine speeds and loads. The powertrain control module (PCM) then adjusts the spark timing based on the amplitude and frequency of the KS signal. The PCM uses the KS signal to calculate the average voltage. Then the PCM assigns a voltage value. The PCM checks the KS and related wiring by comparing the actual knock signal to the assigned voltage range. A normal KS signal should stay outside the assigned voltage range. This diagnostic trouble code (DTC) will set if the KS signal is within the assigned voltage range or not present or if the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system.

Conditions for Running the DTC
    • DTCs P0122, or P0123 are not set.
    • The engine run time is more than 20 seconds.
    • The engine coolant temperature (ECT) is more than 56°C (131°F).
    • The engine speed is between 1,600-6,400 RPM.
    • The manifold absolute pressure (MAP) is more than 60 kPa.

Conditions for Setting the DTC
    • The KS voltage and variation is not within normally expected ranges.
    • The above conditions are present for more than 15 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.

Diagnostic Aids

Inspect the KS for proper installation. A KS that is loose or over torqued may cause the DTC to set.

If this DTC is determined to be intermittent refer to Intermittent Conditions .

Inspect and correct any abnormal engine noise before using the diagnostic table.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: If an engine knock can be heard, repair the engine mechanical condition 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 engine within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed.

Does the scan tool indicate that this diagnostic failed this ignition?

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Go to Step 3

Go to Diagnostic Aids

3
  1. Disconnect the KS harness.
  2. Set the DMM to the 400K-ohm scale.
  3. Measure the resistance of the KS using the DMM connected to a good ground.

Is the resistance of the KS within the specified range?

90-110K ohms

Go to Step 4

Go to Step 6

4
  1. With the DMM still connected, set the DMM to the 400-mV AC hertz scale. Refer to Measuring Frequency in Wiring Systems.

    2. Important: DO NOT tap on plastic engine components.

  2. Tap on the engine block near the appropriate KS while observing the signal indicated on the DMM.

Is any signal indicated on the DMM while tapping on the engine block near the KS?

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Go to Step 5

Go to Step 6

5
  1. Disconnect the PCM connector. Refer to Powertrain Control Module Replacement .
  2. Test the KS signal circuit between the PCM and the KS connector for the following:
    3. • An open
    • A short to voltage
    • A short to ground

Refer to Testing for Continuity , Testing for a Short to Voltage and Testing for Short to Ground in Wiring Systems.

Did you find and correct the condition?

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Go to Step 9

Go to Step 7

6

Replace the KS. Refer to Knock Sensor Replacement .

Did you complete the replacement?

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Go to Step 9

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7
  1. Inspect the KS signal circuit for a poor connection at the PCM or the KS harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If you find a poor connection, repair the connector as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 8

8

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

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Go to Step 9

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9
  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 DTC run and pass?

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Go to Step 10

Go to Step 2

10

With a scan tool, observe the stored information, Capture Info.

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

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Go to Diagnostic Trouble Code (DTC) List

System OK