John Deere 4341.05 – ECU: DEF Dosing Unit Pressure Line Heater, Resistance Too High

The system detects that the electrical resistance in the DEF dosing unit pressure line heater circuit is too high, typically indicating an open circuit. This prevents the heater from functioning properly, which can lead to DEF freezing in cold conditions, affecting DEF injection and emissions control, and may induce an engine derate.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 9RT Series
• 9470RT
• 9520RT
• 9570RT
• 6105M
• 331G
• 333G
• 210G
• 210GLC
• Vermeer D24x40 S3
• Vermeer D40x55 S3
• 4.5L (4045) PowerTech engine
• 6.8L PowerTech engine
• 9.0L (6090) PowerTech engine

1. 1

   Inspect the DEF dosing unit pressure line heater circuit for any damaged, frayed, or loose wiring and connectors.

2. 2

   Inspect all electrical connections and harness components for signs of corrosion, which can artificially increase circuit resistance.

3. 3

   Use a multimeter or diagnostic tool to test the heater element (integrated into the DEF line) for continuity and proper resistance. An open circuit confirms the heater element has failed.

4. 4

   Ensure that the electrical supply to the heater is stable and within John Deere specifications.

1. 1

   Address Wiring Issues

   If the diagnostic checks reveal damaged wiring, loose pins, or corrosion in the harness, repair or replace the affected wiring and clean the connectors.

2. 2

   Replace the DEF Pressure Line

   If the wiring is intact but the heater element itself tests faulty (open circuit), the DEF dosing unit pressure line (which contains the integrated heater) must be replaced.

3. 3

   Clear Codes and Test

   After repairing the wiring or replacing the heated line, reset the ECU to clear the 004341.05 fault code.

4. 4

   Monitor the System

   Run the machine and monitor the DEF system to ensure the heater operates correctly and the engine derate is lifted.