Description:

This diagnostic trouble code is set when the ECU detects that the resistance in the DEF dosing unit return line heater circuit is too high. High resistance typically indicates an open circuit, which can prevent the heater from functioning properly, potentially leading to DEF freezing in the return line in cold conditions.

Reaction:

The ECU may issue warnings or limit DEF system operation to prevent potential damage, impacting DEF injection and overall emissions control efficiency.

Recommendations:

• Inspect Wiring and Connections: Check for any damaged, frayed, or loose wiring and connectors in the DEF dosing unit return line heater circuit. Repair or replace as necessary.
• Test Heater Element: Use diagnostic tools to test the heater element for continuity and proper resistance. Replace the heater if it is faulty.
• Check for Corrosion: Inspect connections and components for signs of corrosion that could increase resistance. Clean or replace corroded parts.
• Verify Electrical Supply: Ensure that the electrical supply to the heater is stable and within specifications.
• Reset ECU and Monitor System: After addressing the issue, reset the ECU to clear the fault code and monitor the system to ensure the heater operates correctly.

Note:

Proper functioning of the DEF dosing unit return line heater is crucial for preventing DEF freezing and ensuring effective DEF injection in cold conditions. Regular inspections and timely maintenance can prevent heater-related issues.