Case IH 19257 – Engine Control Module (ECM): Counter for the lower threshold of Engine coolant downstream temperature

The engine control system has detected the downstream engine coolant temperature dropping below the minimum acceptable threshold for a specific number of counts. This indicates either a genuine engine overcooling condition (such as a stuck-open thermostat) or an implausible/false reading being sent by a failing downstream coolant temperature sensor.

• Tier 4b
• Puma series (150, 165, 175, 185, 200, 220, 240 CVX)
• Optum series (250, 270, 300 CVX)
• Maxxum series
• Steiger series
• Farmall Tier 4B tractors
• Patriot sprayers

1. 1

   Verify actual temperature using an infrared (IR) thermometer on the upper and lower radiator hoses to determine if the engine is genuinely running cold or if the sensor is providing a false reading.

2. 2

   Check coolant levels in the header tank/reservoir and inspect for any visible leaks around the water pump seal, radiator, or hoses.

3. 3

   Inspect the wiring harness and the 2-pin connector going to the downstream coolant temperature sensor for damaged wires, corrosion, or an open/short circuit.

4. 4

   If the IR thermometer confirms the engine is running cold, inspect the thermostat (water temperature regulator) as it is likely stuck in the open position.

5. 5

   Check the DEF Heater Valve (Coolant Control Valve) to ensure it is not stuck open, which can disrupt normal cooling system temperatures by continuously circulating hot coolant to the DEF tank.

1. 1

   Cool Down

   Turn off the tractor and allow the engine to cool completely to relieve cooling system pressure and prevent severe burns.

2. 2

   Relieve Pressure

   Slowly remove the cap on the coolant header tank to relieve any residual pressure.

3. 3

   Address Thermostat (If Applicable)

   If diagnostics proved the engine is genuinely overcooling, remove the thermostat housing, extract the stuck thermostat, clean the mating surfaces, and install a new thermostat and gasket.

4. 4

   Replace the Sensor (If Applicable)

   If the engine temperature is normal but the gauge/ECM reads cold, the sensor has failed. Disconnect the electrical connector from the downstream coolant temperature sensor.

5. 5

   Remove Old Sensor

   Unthread the faulty brass sensor from the block/housing. Have a catch pan ready, as you will lose some coolant during this step.

6. 6

   Install New Sensor

   Thread the new sensor into place. Caution: Do not overtighten the sensor, as the brass threads can easily break off inside the housing.

7. 7

   Reconnect and Refill

   Reconnect the 2-pin wiring harness. Top up the engine coolant in the header tank to replace whatever was lost.

8. 8

   Reboot and Clear

   Turn the tractor's battery disconnect off and back on to reboot the system. Clear the fault codes via the AFS Pro display or diagnostic tool. Run the tractor up to operating temperature to ensure the code does not return and there are no leaks.