Kubota P0326 – Engine Control Module (ECM) / Powertrain Control Module (PCM): Knock 1 Excessive or Erratic Signal

The ECM detects that the reference voltage from the knock sensor has fallen outside the accepted threshold, meaning the signal is either out of range, erratic, or not performing as anticipated. When this happens, the ECM cannot reliably detect engine knock (pre-detonation) to properly adjust ignition timing.

• Kubota WG1605
• Kubota WG2503
• Kubota WG3600
• Kubota WG3800
• Multiquip LS300GK

1. 1

   Verify fuel quality to ensure the engine is running on the correct octane fuel, as low octane can cause actual knocking.

2. 2

   Inspect the knock sensor's electrical connector for moisture, corrosion, bent pins, or a loose connection.

3. 3

   Trace the wiring harness back to the ECM to check for fraying, cuts, or rodent damage.

4. 4

   Perform a tap test using an OBD-II scan tool to monitor live data while lightly tapping the engine block near the sensor to check for a voltage spike.

5. 5

   Use a multimeter to verify the 5-volt reference signal, ground integrity at the sensor connector, and test the sensor's resistance.

1. 1

   Preparation

   Turn the vehicle/machine to the OFF position and disconnect the negative battery cable.

2. 2

   Locate the Sensor

   Locate the knock sensor on the engine block. On Kubota WG series engines, it is typically mounted directly to the side of the cylinder block.

3. 3

   Disconnect

   Carefully unplug the electrical connector from the knock sensor.

4. 4

   Removal

   Use the appropriate socket to unthread and remove the faulty knock sensor from the engine block.

5. 5

   Installation

   Thread the new knock sensor into the block by hand to prevent cross-threading. Torque the sensor exactly to the manufacturer's specifications (over-tightening can crush the internal piezoelectric element and ruin the new sensor).

6. 6

   Reassembly

   Reconnect the electrical connector and the negative battery cable.

7. 7

   Clear Codes

   Turn the machine to the ON mode and use a diagnostic scan tool to clear the P0326 DTC from the ECM. Run the engine to verify the code does not return.