Kubota P0118 – Engine Control Module (ECM): Engine Coolant Temperature (ECT) Sensor Circuit High Input

The Engine Control Module (ECM) detects an abnormally high voltage signal from the Engine Coolant Temperature (ECT) sensor, indicating high resistance and making the ECM believe the engine coolant is extremely cold. This is most commonly caused by an open circuit, a disconnected sensor, damaged wiring, or a failed sensor.

• L-Series
• L4701
• M-Series
• B-Series
• LX-Series
• K/KX-Series
• KX71
• KX91
• K008-3
• U-Series
• RTV-X Series
• RTV-X900
• RTV-X1100
• RTV-X1120
• RTV-X1140
• F-Series
• D-Series
• D902
• D1005
• D1105
• V-Series
• V1505
• V2003
• V2403
• B26
• B2301
• B2601
• L2250
• L3450
• L4200
• M4900
• M6800
• B2400
• B7800
• KH-Series
• KX101
• KX151
• F2000
• F2100
• R-Series

1. 1

   Use a diagnostic scan tool to confirm the P0118 code and view live freeze-frame data. If the ECT reading is exactly -40°F (or -40°C), it indicates an open circuit.

2. 2

   Inspect the ECT sensor (near thermostat housing or cylinder head) for a disconnected plug, corroded connector pins, or broken wiring.

3. 3

   Verify that the engine coolant is at the proper level, as low coolant can cause poor sensor contact and erratic readings.

4. 4

   With the ignition ON and engine OFF, backprobe the sensor connector to verify the ECM is supplying a ~5V reference voltage and a good ground.

5. 5

   Disconnect the sensor and jump the two connector pins together. If the scanner output shows a very high temperature (above 284°F), the wiring and ECM are functioning correctly, confirming a faulty sensor.

6. 6

   Measure the resistance of the ECT sensor across its terminals at different temperatures and compare it to the Kubota specification chart. Infinite resistance indicates an open internal circuit.

1. 1

   Prep the Machine

   Ensure the engine is completely cool and the machine is parked on a level surface. Disconnect the negative battery terminal to prevent electrical shorts.

2. 2

   Locate the Sensor

   Find the ECT sensor on the engine block or thermostat housing.

3. 3

   Disconnect Wiring

   Carefully depress the locking tab on the electrical pigtail and unplug the connector from the sensor. If the connector is heavily corroded, splice in a new replacement pigtail.

4. 4

   Remove the Sensor

   Place a catch pan under the engine to catch any escaping coolant. Use a deep socket or wrench on the hex-head of the brass sensor to unthread it from the coolant passage.

5. 5

   Install the New Sensor

   Thread the new OEM Kubota ECT sensor into the port. Tighten it to the manufacturer's specified torque (do not overtighten, as it is a brass fitting).

6. 6

   Reconnect

   Plug the electrical connector back into the new sensor until it clicks securely.

7. 7

   Refill Coolant

   Top off the radiator/overflow tank with the correct Kubota-approved coolant to replace any that was lost during the swap.

8. 8

   Clear Codes and Test

   Reconnect the battery. Turn the ignition on, use your OBD-II scanner to clear the P0118 fault code, and start the engine. Monitor the dash temperature gauge and live scanner data as the engine warms up to ensure the reading climbs smoothly and the cooling fans engage properly.