Case IH F-3507-04 - ECU – Engine Control Unit (ECU): Supply UB1 short circuit to ground failure

The UB1 circuit is the dedicated voltage supply line for the internal electrical heaters inside the DEF/AdBlue Pump Module (Dosing Control Unit). The system uses these heaters to thaw or prevent diesel exhaust fluid from freezing. This code sets when the controller detects that the UB1 voltage supply line has shorted directly to a ground source, either within the wiring harness or internally within the pump module itself.

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1. 1

   Verify Fault Status: Connect the CNH Electronic Service Tool (E.A.S.Y. or PT-Box) to verify if F-3507-04 is currently active or stored as an intermittent historical code.

2. 2

   Harness Inspection: Visually inspect the wiring harness running from the ECU to the DEF/AdBlue pump module. Look for chafing, melted insulation, or pinch points against the machine's chassis that could cause the UB1 wire to ground out.

3. 3

   Circuit Isolation Test: Disconnect the electrical connector at the DEF pump module. Turn the key switch ON (engine off) and use a multimeter to check the UB1 supply pin on the harness side for a short to ground.

4. 4

   Component Testing: If the harness tests good (no short to ground when disconnected), the short is likely internal to the DEF pump module's heating element. Test the pump module's heater pins for internal continuity to the module housing/ground.

1. 1

   Power Down

   Turn the key switch to the OFF position (Key 15 off) and disconnect the machine's battery to prevent electrical spikes.

2. 2

   Address the Short Circuit

   If the harness is damaged: Repair the chafed/shorted wire using an approved CNH wiring repair kit, or replace that section of the SCR harness. Ensure the new wiring is routed away from sharp frame edges or high-heat exhaust components. If the pump module is internally shorted: The internal heaters cannot be serviced separately. You must remove the DEF/AdBlue pump module lines and mounting hardware, and replace the entire pump module assembly.

3. 3

   Reassembly

   Reconnect the DEF lines and the electrical connector to the pump module. Reconnect the battery.

4. 4

   Clear and Verify

   Connect the diagnostic tool, clear the F-3507-04 fault code, and cycle the key. Start the engine and allow the SCR system to initialize and run its heater checks to verify the repair was successful and the code does not return.