Kubota P0420 – Engine Control Unit (ECU) / Engine Control Module (ECM): DPF intermediate temperature sensor temperature abnormal low temperature

The sensor monitoring the middle section of the Diesel Particulate Filter (DPF) is reporting an impossibly low temperature to the computer. When this data is lost or out of range, the machine cannot properly manage the DPF regeneration cycle, which often results in active regeneration failure, continuous attempts to regenerate, or engine derating.

• SVL65-2
• SVL75-2
• SVL90-2
• SVL95-2s
• SVL97-2
• KX040-4
• KX060-5
• U50-5
• U56-5
• S590
• S750
• T595
• T870
• TB240
• TB280FR
• SK1050

1. 1

   Verify the Sensor Position: Kubota DPF systems use multiple exhaust temperature sensors (typically designated as Thermo 0, Thermo 1, and Thermo 2). The 'intermediate' sensor is usually the Thermo 2 (T2) position. Check your specific machine's service manual to confirm the exact location.

2. 2

   Inspect the Wiring Harness: Check the wiring and the connector going to the DPF intermediate temperature sensor. Look for physical damage, tampering, or corrosion that could cause an open circuit (which the ECU interprets as an abnormally low temperature).

3. 3

   Check for Accompanying Codes: Look for related circuit codes such as P1434 (DPF intermediate temperature sensor high voltage), P1435 (low voltage), or P1426 (abnormal high temperature) which can help isolate whether the issue is the sensor itself or the wiring.

4. 4

   Live Data Monitoring: If you have a diagnostic tool, monitor the live exhaust temperature data. If the intermediate sensor reads a static, extremely low temperature even when the exhaust is hot, the sensor has likely failed internally.

1. 1

   Locate the Sensor

   Identify the DPF intermediate temperature sensor (Thermo 2) on the DPF exhaust aftertreatment housing.

2. 2

   Disconnect

   Unplug the sensor's electrical connector from the main engine wiring harness.

3. 3

   Remove

   Unscrew the faulty temperature sensor from the DPF housing. (Note: The thread size is typically M12 metric; penetrating oil may be required if the sensor is seized from exhaust heat).

4. 4

   Install

   Thread the new genuine Kubota DPF Thermo Sensor into the housing and tighten it to the manufacturer's torque specification.

5. 5

   Reconnect

   Plug the new sensor's 12-inch wire connector back into the engine harness.

6. 6

   Clear Codes and Reset

   Use a dealer-level diagnostic tool (or equivalent software) to clear the P0420 code. You may also need to perform a soot load reset.

7. 7

   Test

   Initiate a forced/stationary DPF regeneration to verify that the new sensor is reading correctly and that the regeneration cycle completes successfully without throwing the code again.