Case IH F-5435-31 - ECU – Engine Control Unit (ECU): DEF/AdBlue supply module pump temperature is too low to activate pump

The DEF supply module internal temperature sensor reports a temperature below the safe operating threshold, causing the system to lock out the pump to prevent mechanical damage. This condition is typically caused by actual freezing conditions where the heater circuit has failed to thaw the fluid, or a failed internal temperature sensor/circuit falsely reporting a low temperature.

• MAGNUM AFS Connect
• Magnum (180-370)
• Steiger (350-600)
• Puma (130-215)
• Maxxum (110-140)
• Austoft 9900 Sugarcane Harvesters
• Axial-Flow Combines (5130-9230 series)
• Patriot (4430)
• Titan series
• Farmlift Telehandlers (632, 635, 735)

1. 1

   Plausibility Check: Connect a diagnostic scan tool and view the live data for the DEF supply module temperature. Compare this reading to the ambient air temperature and the DEF tank temperature. If the machine is in a warm shop but the sensor reads below freezing, the internal sensor is faulty.

2. 2

   Visual & Physical Inspection: If operating in freezing conditions, check if the DEF tank and lines are physically frozen.

3. 3

   Wiring Harness Check: Inspect the electrical harness and connectors between the ECU and the DEF Supply Module for corrosion, moisture intrusion, or damaged pins.

4. 4

   Heater Circuit Test: Test the DEF supply module heater circuit and the DEF tank heater for proper voltage and continuity. If the heater is shorted or open, it will fail to thaw the fluid, triggering the temperature lock-out.

1. 1

   Power down system

   Turn off the ignition and wait for the ECU to completely power down and finish any purge cycles.

2. 2

   Disconnect battery

   Disconnect the negative battery cable.

3. 3

   Locate module

   Locate the DEF Supply Module (often mounted near the DEF tank or on the frame rail).

4. 4

   Clean area

   Thoroughly clean the area around the module to prevent dirt from entering the SCR system.

5. 5

   Disconnect electrical connector

   Disconnect the main electrical connector from the module.

6. 6

   Disconnect DEF lines

   Disconnect the DEF suction, pressure, and return lines. Have a clean catch pan ready, as residual DEF will spill.

7. 7

   Remove faulty module

   Unbolt the mounting hardware and remove the faulty DEF supply module.

8. 8

   Install new module

   Install the new DEF supply module and torque the mounting bolts to OEM spec.

9. 9

   Reconnect lines and connector

   Reconnect the DEF lines (ensure they click/lock into place) and the electrical connector.

10. 10

    Replace filter

    It is highly recommended to replace the DEF supply module filter (main filter) during this service.

11. 11

    Clear fault code

    Reconnect the battery, turn on the ignition, and use a diagnostic scan tool to clear the F-5435-31 fault code.

12. 12

    Run prime/dosing test

    Run a DEF system prime/dosing test via the scan tool to verify the pump builds target pressure (approx. 500 kPa / 72.5 PSI) and check for leaks.