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P code powertrain Medium severity

P20C6 Reductant Heater "D" Control Circuit Performance

The OBD2 code P20C6 indicates a performance issue with the control circuit for the reductant heater "D," which is part of the diesel exhaust fluid (DEF) system.

Definition

The OBD2 code P20C6 indicates a performance issue with the control circuit for the reductant heater "D," which is part of the diesel exhaust fluid (DEF) system. This code suggests that the heater is not functioning properly, potentially affecting the operation of the selective catalytic reduction (SCR) system

Common causes

  • Faulty reductant heater
  • Open or shorted wiring in the control circuit
  • Poor electrical connections
  • Failed control module
  • Faulty temperature sensor
  • Issues with the power supply to the heater
  • Corroded connectors or terminals

Common misdiagnoses

  • Faulty reductant heater
  • Wiring issues or shorts in the circuit
  • Defective engine control module (ECM)
  • Incorrectly diagnosed fuel system issues
  • Misinterpretation of related codes
  • Faulty sensors (e.g., temperature or pressure sensors)
  • Issues with the DEF (diesel exhaust fluid) quality or level
  • Problems with the exhaust aftertreatment system

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are multiple issues

  2. 2. Inspect the Reductant Heater

    Locate the reductant heater and visually inspect it for any signs of damage, corrosion, or loose connections

  3. 3. Check the wiring harness and connectors for any frayed wires, corrosion, or poor connections

  4. 4. Test the Reductant Heater

    Use a multimeter to test the resistance of the reductant heater. Compare the readings to the specifications provided in the vehicle’s service manual

  5. 5. If the resistance is out of range, the heater may be faulty and require replacement

  6. 6. Check the Control Circuit

    Inspect the control circuit for the reductant heater. This includes checking the fuses, relays, and any associated wiring

  7. 7. Ensure that the ECM is sending the correct signals to the heater. You may need to use a scan tool to monitor the heater control circuit while the engine is running

  8. 8. Inspect the DEF System

    Check the DEF tank and lines for any leaks or blockages that could affect the heater's performance

  9. 9. Ensure that the DEF fluid is at the correct level and is not contaminated

  10. 10. Check for Software Updates

    Sometimes, manufacturers release software updates for the ECM that can resolve issues related to the reductant system. Check with the dealership or manufacturer for any available updates

  11. 11. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner

  12. 12. Take the vehicle for a test drive to see if the code returns. Monitor the performance of the DEF system during the drive

  13. 13. Consult a Professional

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with diesel exhaust systems and OBD-II diagnostics.Conclusion Troubleshooting OBD-II code P20C6 involves a systematic approach to inspect and test the reductant heater and its control circuit. By following these steps, you can identify and resolve the underlying issue effectively