Case IH 19420 – Engine Control Unit (ECU): Measured coolant temperature different to modeled coolant temperature

This is a plausibility fault. The Engine Control Unit (ECU) calculates a 'modeled' or expected coolant temperature based on operating conditions (such as engine load, ambient temperature, and run time). If the actual temperature reported by the Engine Coolant Temperature (ECT) sensor deviates significantly from this modeled value, the ECU logs fault code 19420. This typically points to a faulty sensor, a wiring issue, or a mechanical cooling system issue (like a thermostat stuck open causing the engine to run too cool).

• Tier 4b
• Case 580N
• Case 580SN
• Case 580SN WT
• Case 590SN

1. 1

   Verify that the engine coolant is at the proper level.

2. 2

   Ensure the engine thermostat is not stuck open, which can cause the engine to be over-cooled (especially under light loads), triggering the plausibility fault.

3. 3

   Disconnect the coolant temperature sensor and the ECU connectors and measure the resistance from the coolant temperature sensor pins to the corresponding ECU connector pins (should be less than 10 ohms).

4. 4

   Wiggle the wiring harness during the multimeter measurement to reveal any intermittent shorts or open circuits.

5. 5

   Test the sensor's resistance at known temperatures to see if it is reading out of range (0 °C = 7500 Ω, 20 °C = 4200 Ω, 60 °C = 780 Ω, 100 °C = 280 Ω).

1. 1

   Cool down machine

   Safely park the machine, turn off the engine, and allow the engine and coolant to cool completely to avoid burns.

2. 2

   Disconnect battery

   Disconnect the battery ground strap/cable to prevent electrical damage.

3. 3

   Locate sensor

   Locate the engine coolant temperature sensor on the engine block/water outlet.

4. 4

   Disconnect wiring

   Disconnect the electrical wiring harness connector from the coolant temperature sensor.

5. 5

   Drain coolant

   Drain a small amount of coolant from the system to drop the fluid level below the sensor port, or be prepared to quickly swap the sensor to minimize fluid loss.

6. 6

   Remove sensor

   Unscrew and remove the faulty coolant temperature sensor.

7. 7

   Install new sensor

   Install the new coolant temperature sensor and tighten it to the manufacturer's specified torque.

8. 8

   Reconnect wiring

   Reconnect the electrical wiring harness to the new sensor.

9. 9

   Refill coolant

   Refill the engine coolant to the correct level and bleed any air from the cooling system.

10. 10

    Reconnect battery

    Reconnect the battery ground cable.

11. 11

    Test and clear codes

    Start the engine, allow it to reach normal operating temperature, check for leaks, and use a diagnostic tool to clear the fault code.