Kubota P0337 – Engine Control Module (ECM) / Engine ECU: Loss of Crankshaft Input Signal

This code is triggered when the Engine Control Module (ECM) detects that the signal voltage from the crankshaft position sensor (CKP) has dropped below the acceptable threshold or is entirely missing. The ECM relies on this pulsed voltage signal to determine the exact rotational speed (RPM) and position of the crankshaft. Without this data, the engine computer becomes 'blind' and cannot properly synchronize fuel injection and ignition timing.

• SVL75
• SVL90
• SK1050
• KX040-4
• KX040-5
• L3901
• L3970
• L3902
• MX4900
• M-Series

1. 1

   Visual Inspection: Inspect the crankshaft position sensor, its wiring harness, and the connector. Look for frayed wires, rodent damage, loose pins, or heavy corrosion.

2. 2

   Contamination Check: Check the sensor end for heavy buildup of oil, metallic debris, or dirt, which can block the magnetic signal.

3. 3

   Voltage & Ground Test: With the key ON (engine off), backprobe the sensor connector using a digital multimeter (DVOM) to confirm it is receiving proper reference voltage and has a solid ground to the chassis/ECM.

4. 4

   Signal Verification: While cranking the engine, use an oscilloscope (preferred) or a multimeter to measure the signal wire. You should see a stable waveform or fluctuating AC voltage. If the voltage remains flat or excessively low, the sensor is likely dead.

5. 5

   Mechanical Inspection: If the sensor and wiring test good, inspect the reluctor wheel (tone ring) on the crankshaft for missing teeth, damage, or misalignment.

1. 1

   Disconnect Power

   Disconnect the negative battery cable to prevent electrical shorts during the repair.

2. 2

   Locate the Sensor

   Locate the Crank Angle Sensor on the engine block (typically mounted near the crankshaft pulley or flywheel housing). You may need to remove a protective cover (Crank Sensor Cover) to access it.

3. 3

   Disconnect the Harness

   Press the release tab and carefully unplug the electrical connector from the sensor.

4. 4

   Remove the Sensor

   Remove the M6 flange bolt securing the sensor to the engine block. Gently twist and pull the sensor straight out of its bore.

5. 5

   Clean the Port

   Wipe the mounting surface and the sensor bore clean with a lint-free rag. Ensure no dirt or debris falls into the engine.

6. 6

   Install the New Sensor

   Lightly lubricate the O-ring on the new sensor with clean engine oil. Push it into the bore until it seats fully.

7. 7

   Secure and Reconnect

   Install and tighten the M6 flange bolt. Reconnect the electrical wiring harness until it clicks into place.

8. 8

   Clear Codes

   Reconnect the battery. Use an OBD-II or Kubota diagnostic scan tool to clear the P0337 fault code from the ECM.

9. 9

   Test Run

   Start the engine and verify that it idles smoothly and the Check Engine light does not return.