Case IH 3173 (DTC F623) - ECU – Engine Control Unit (ECU): Engine coolant temperature has exceeded the warning threshold

The system monitors the engine coolant temperature via a dedicated sensor (B-016). The system has two thresholds to signal high engine temperature: Pre-warning (exceeds 106.0 °C / 222.7 °F) and Warning (Fault 3173/F623: exceeds 110.0 °C / 229.9 °F).

• MAXXUM T4E
• 240 Series Axial-Flow Combines
• Puma Series (130 through 240)
• Maxxum Series (100 through 150)
• Farmall Series (85C, 95, 105U)
• Magnum Series
• Case construction equipment

1. 1

   Coolant Level: Verify that the engine coolant is at the proper level in the expansion tank.

2. 2

   Cooling Package Inspection: Check the radiator, intercooler, and condenser for blockages, dust buildup, or debris that could restrict airflow.

3. 3

   Sensor Wiring & Connector: Inspect the wiring harness and the electrical connector at the coolant temperature sensor for corrosion, moisture intrusion, or short circuits.

4. 4

   Sensor Testing: Test the resistance of the coolant temperature sensor. The sensor works by varying electrical resistance as the temperature changes. If the resistance is out of specification for the ambient temperature, the sensor is faulty.

5. 5

   Mechanical Checks: Verify the operation of the engine thermostat (ensure it is opening) and the water pump.

1. 1

   Cool Down

   Allow the engine to cool completely to prevent severe burns from hot coolant.

2. 2

   Relieve Pressure

   Slowly remove the radiator/expansion tank cap to relieve any residual cooling system pressure.

3. 3

   Disconnect

   Locate the engine coolant temperature sensor on the engine block or cylinder head and carefully disconnect its electrical connector.

4. 4

   Remove Sensor

   Unscrew the faulty sensor. Note: Be prepared for some coolant loss when the sensor is removed; have a catch pan ready.

5. 5

   Install New Sensor

   Thread the new OEM coolant temperature sensor into place and tighten it to the manufacturer's torque specification.

6. 6

   Reconnect

   Reattach the electrical connector, ensuring it clicks securely into place to withstand engine vibration.

7. 7

   Refill & Bleed

   Top off the engine coolant to the correct level.

8. 8

   Test

   Start the engine, check for leaks around the new sensor, and use a diagnostic tool (EST) to clear the fault code.