ECU 005435.11 – DEF Dosing Unit Pump Circuit Fault. John Deere System Advisory.

ECU 005435.11 (ECU 5435.11)

Code: 005435.11

Shortcode: 5435.11


This diagnostic trouble code indicates that the DEF dosing unit pump motor is unable to build pressure when priming. This condition can affect the proper functioning of the DEF dosing system.


The ECU may limit or adjust the operation of the DEF dosing system to manage the inability to build pressure and ensure safe operation of the emissions control system.


  • Inspect DEF Pump Wiring and Connections: Check for damaged, frayed, or loose wiring and connectors associated with the DEF dosing unit pump. Repair or replace as necessary.
  • Test DEF Pump Function: Use diagnostic tools to test the DEF dosing unit pump for proper operation and pressure build-up. Replace the pump if it is faulty.
  • Check for Blockages: Inspect the DEF system for any blockages or restrictions that might prevent the pump from building pressure.
  • Verify Electrical Supply: Ensure that the electrical supply to the DEF dosing unit pump is stable and within specifications.
  • Reset ECU and Monitor System: After resolving the issue, reset the ECU to clear the fault code and monitor the system to ensure normal operation.


Proper operation of the DEF dosing unit pump is crucial for accurate DEF dosing and emissions control. Regular inspections and timely maintenance can help prevent pressure-related issues.

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