Case IH F-4376-03 - ECU – DCU (Dosing Control Unit) or Engine ECU (Engine Control Unit): DEF/AdBlue reverting valve driver circuit short to battery failure

The reverting valve inside the DEF Supply Module reverses DEF flow when the engine shuts down to purge fluid. FMI 03 indicates the control module detected measured current on the reverting valve driver circuit is higher than expected when active, indicating a wiring harness short to battery voltage or an internal short in the reverting valve's electrical coil.

• MAGNUM AFS Connect
• Axial-Flow 240 Series
• Axial-Flow 5130
• Axial-Flow 6130
• Axial-Flow 7130
• Axial-Flow 7230
• Axial-Flow 8230
• Axial-Flow 9230
• Magnum (180–370)
• Steiger (350–600)
• Maxxum (110–140)
• Puma (130–215)
• Farmall series
• Patriot 4430
• Titan series
• Farmlift series

1. 1

   Visually inspect the wiring harness between the Engine ECU/DCU and the DEF Supply Module for chafed wire insulation, melted looms, or pinched wires that could bridge the reverting valve control wire to a power wire.

2. 2

   Disconnect the DEF Supply Module connector and check for corrosion, bent pins, or DEF fluid intrusion (DEF can wick up the harness and cause shorts).

3. 3

   With the key ON and engine OFF, use a multimeter to test the reverting valve signal wire at the pump connector for voltage. If battery voltage is present when the ECU is not commanding the valve, the harness is shorted to power.

4. 4

   If the wiring harness tests good and shows no shorts to battery, the short is internal to the reverting valve coil inside the DEF Supply Module.

1. 1

   Power Down

   Turn off the ignition. Wait at least 5 to 10 minutes before disconnecting the battery so the aftertreatment system can complete its purge cycle and save data to the ECU.

2. 2

   Disconnect Battery

   Disconnect the negative battery cable to ensure safety and prevent electrical spikes.

3. 3

   Locate the Module

   Locate the DEF Supply Module (usually mounted directly to the DEF tank or on the frame rail nearby).

4. 4

   Clean the Area

   Thoroughly clean the exterior of the module and surrounding fittings. DEF systems are highly sensitive to dirt and contaminants.

5. 5

   Disconnect Lines

   Disconnect the electrical connector and the DEF fluid lines (suction, pressure, and return/backflow). Have a clean catch pan ready, as some DEF will spill.

6. 6

   Remove Module

   Remove the mounting bolts securing the DEF Supply Module to its bracket and remove the unit.

7. 7

   Install New Module

   Mount the replacement DEF Supply Module and tighten the bolts to OEM specifications.

8. 8

   Reconnect

   Reconnect the DEF fluid lines (listen for the quick-connects to 'click' into place) and plug in the electrical connector.

9. 9

   Clear Codes & Test

   Reconnect the battery. Turn the key ON, connect a diagnostic scan tool, and clear the F-4376-03 fault code. Run a DEF system leak test or prime routine via the scan tool to ensure the pump builds pressure (typically around 9 bar / 130 psi) and there are no leaks.