Kubota P0117 – Engine Control Unit (ECU) / Engine Control Module (ECM): ECT/CHT Low Voltage

The ECU detects that the voltage signal from the ECT sensor has dropped below the minimum threshold (typically less than 0.10V or 0.20V) for longer than 1 to 2 seconds, indicating a sensor malfunction, an internal short in the sensor, or a short-to-ground in the sensor's wiring harness.

• V3800
• V2403
• V1505
• D1105
• D1803
• WG972
• WG1605
• WG3800
• M108X
• M108S
• L-Series
• B-Series
• RTV-X900
• RTV-X1100
• RTV-X1120
• RTV-X1140
• KX series
• K008 series
• Toro mowers
• Genie lifts
• Baroness equipment
• forklifts

1. 1

   Visually inspect the ECT sensor connector and wiring harness for physical damage, corrosion, or exposed wires that could be shorting to the engine block (ground).

2. 2

   Perform a voltage reference check: Disconnect the ECT sensor and turn the key ON (Engine OFF). Measure the voltage at the signal wire on the harness connector. The ECU should supply a 5.00V reference signal. If 5.00V is present, the sensor is internally shorted. If voltage is 0V or significantly low, there is a short-to-ground in the wiring harness between the sensor and the ECU, or the ECU is faulty.

3. 3

   Verify the fault using Kubota Diagmaster or a compatible scan tool by monitoring the ECT voltage PID. If it reads less than 0.10V with the key ON, the fault is active.

1. 1

   Preparation

   Turn the key switch to the OFF position and allow the engine to cool completely to avoid burns from hot coolant.

2. 2

   Locate the Sensor

   The ECT sensor is typically threaded into the engine cylinder head or the water flange/thermostat housing.

3. 3

   Remove the Sensor

   Disconnect the electrical wire connector from the sensor. Using a deep socket or open-ended wrench, carefully unscrew the sensor. Note: Have a catch pan ready, as a small amount of coolant will leak out.

4. 4

   Install the New Sensor

   Thread the new brass ECT sensor into the housing. Tighten to the manufacturer's torque specification (do not overtighten, as brass threads can break).

5. 5

   Reconnect

   Plug the electrical connector back into the new sensor.

6. 6

   Refill Coolant

   Top off the engine coolant reservoir/radiator to replace any fluid lost during the swap.

7. 7

   Clear Codes

   Connect your diagnostic scanner, clear the P0117 DTC, and run the engine to operating temperature to verify the code does not return and the dashboard temperature gauge reads accurately.