John Deere 5435.09 – ECU: CAN Bus Message Cannot Be Received, Information from DEF Dosing Unit.

There is a data transfer or communication problem between the Engine Control Unit (ECU) and the Diesel Exhaust Fluid (DEF) dosing unit pump. The ECU is not receiving the expected CAN bus messages from the DEF pump module, which typically results in an engine power derate, increased fuel consumption, and the machine refusing to perform regeneration cycles.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 9470RT
• 9520RT
• 9570RT
• 6105M
• 210L
• 310L
• 310SL
• 315SL
• 410L
• 710L
• 130G
• 350G LC
• 344L
• 337E
• 437E

1. 1

   Inspect the wiring harness and connectors associated with the DEF dosing unit pump for damage, fraying, corrosion, or loose pins.

2. 2

   Ensure that the electrical supply to the DEF dosing unit pump is stable, within specifications, and that the module has a solid ground connection.

3. 3

   Test the CAN bus communication lines between the ECU and the DEF dosing unit for continuity and ensure there are no shorts to ground or power.

4. 4

   Use a John Deere diagnostic tool (Service ADVISOR) to ping the DEF dosing unit pump and run an active test for proper operation and pressure build-up.

5. 5

   Inspect the DEF system lines and injector for any blockages, crystallized DEF deposits, or restrictions that might be causing secondary pressure issues.

1. 1

   Repair Wiring

   If the diagnostic checks reveal damaged wiring or poor connections on the CAN bus or power lines, repair or replace the affected harness sections.

2. 2

   Replace the DEF Dosing Unit Pump

   If the wiring, power, and ground are all verified as good but the ECU still cannot communicate with the DEF dosing unit, the internal controller of the DEF pump has likely failed. Remove and replace the DEF Dosing Unit Pump assembly.

3. 3

   Reassemble and Prime

   Install the new pump, reconnect the DEF lines and electrical harnesses, and ensure the DEF tank is filled with clean, ISO 22241-certified DEF.

4. 4

   Clear Codes and Reset

   Use a diagnostic tool to reset the ECU, clear the 005435.09 fault code, and prime the DEF system.

5. 5

   Monitor System

   Run the machine and monitor the system to ensure normal operation and verify that the machine can successfully perform a regeneration cycle.