Description:

This diagnostic code is triggered when the resistance in the DEF dosing unit return line heater circuit is detected to be too low. Low resistance typically indicates a short to ground, which can cause the heater to malfunction or fail.

Reaction:

The ECU may limit or adjust the operation of the DEF system to prevent potential damage, which can impact the efficiency of DEF injection and overall vehicle performance.

Recommendations:

• Inspect Wiring and Connections: Check for 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 proper resistance. Replace the heater if it is faulty.
• Check for Short Circuits: Inspect the circuit for points where wires may be touching ground, causing a short circuit. Repair or insulate as needed.
• Verify Electrical Supply: Ensure that the electrical supply to the heater 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.

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 maintenance and timely repairs can help avoid resistance-related problems.