Case IH 3903 (DTC 1A15) - ECU – Engine Control Unit (ECU): Fuel temperature is too high

The system has detected that the physical signal from the Fuel Temperature Sensor is above the maximum allowed limit. Hot fuel loses its lubrication properties, which can cause severe damage to the high-pressure injector pump. The engine output and maximum power level are typically derated to protect the system.

• MAXXUM T4E
• Case IH 240 Series Axial-Flow Combines
• Case IH Farmall Tractors (40, 45, 50, 115U, 115C)
• Case IH Magnum Tractors
• Case IH CX, C, CS Pro, and Maxxum MX Series Tractors

1. 1

   Check the fuel level and temperature in the tank (if nearly empty, hot return flow can rapidly heat the remaining fuel)

2. 2

   Use a diagnostic tool to check the sensor's voltage for plausibility (out of range high points to a faulty device or wiring issue)

3. 3

   Inspect the wiring harness and connector at the fuel temperature sensor for shorts to battery voltage, shorts to ground, or intermittent electrical connections

4. 4

   Check for fuel inlet or return restrictions, and verify the fuel supply pressure to the high-pressure pump

1. 1

   Fill the Fuel Tank

   If the tank is low, fill it with fresh diesel. This will cool the overall fuel volume and may resolve the overheating condition if it was caused by hot return fuel.

2. 2

   Test Run

   Run the machine temporarily to see if the temperature drops and the code clears. If the code persists, proceed to electrical testing.

3. 3

   Test the Sensor/Wiring

   Disconnect the fuel temperature sensor (often located on the fuel filter housing) and test the circuit for proper voltage and continuity back to the ECU.

4. 4

   Replace the Sensor

   If the wiring is intact but the sensor is reading out of range or failing the ECU startup check, replace the Fuel Temperature Sensor.

5. 5

   Clear Codes

   Reconnect the new sensor, clear the fault codes from the ECU, and run the engine to verify that the fuel temperature registers within the normal operating range.