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P code powertrain Medium severity

P20C2 Reductant Heater "C" Control Circuit Performance

The OBD2 code P20C2 indicates a performance issue with the control circuit for the reductant heater "C," which is part of the diesel exhaust fluid (DEF) system.

Definition

The OBD2 code P20C2 indicates a performance issue with the control circuit for the reductant heater "C," 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 "C"
  • Open or shorted wiring in the control circuit
  • Poor electrical connections
  • Failed control module
  • Blown fuse related to the reductant heater
  • Corroded connectors
  • Malfunctioning temperature sensor
  • Software issues in the engine control module (ECM)

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 (e.g., P20C1, P20C3)
  • Problems with the DEF (diesel exhaust fluid) quality or level
  • Issues with the exhaust system or sensors
  • Faulty temperature sensors
  • Misdiagnosed injector problems
  • Battery or charging system issues affecting performance

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

  3. 3. Visually inspect the reductant heater for any signs of damage, corrosion, or physical wear

  4. 4. Ensure that the heater is properly connected and that there are no loose or damaged wires

  5. 5. Test the Reductant Heater

  6. 6. Use a multimeter to check the resistance of the reductant heater. Compare the readings to the manufacturer's specifications. If the resistance is out of range, the heater may need to be replaced

  7. 7. Check the Control Circuit

  8. 8. Inspect the wiring and connectors in the control circuit for any signs of damage, corrosion, or loose connections

  9. 9. Use a multimeter to test for continuity in the wiring between the ECM (Engine Control Module) and the reductant heater

  10. 10. Inspect the ECM

  11. 11. Ensure that the ECM is functioning properly. If there are issues with the ECM, it may not be sending the correct signals to the reductant heater

  12. 12. Check for any software updates or recalls related to the ECM

  13. 13. Check for Voltage Supply

  14. 14. With the ignition on (engine off), use a multimeter to check for voltage at the reductant heater connector. If there is no voltage, trace the circuit back to the ECM to identify where the issue may lie

  15. 15. Examine the DEF System

  16. 16. Ensure that the DEF tank is filled with the correct fluid and that there are no blockages in the DEF lines

  17. 17. Check for any leaks or contamination in the DEF system

  18. 18. Clear Codes and Test Drive

  19. 19. After performing repairs or inspections, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  20. 20. Consult Technical Service Bulletins (TSBs)

  21. 21. Check for any TSBs related to the P20C2 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues that can assist in troubleshooting

  22. 22. Seek Professional Help

  23. 23. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with diesel engines and SCR systems. By following these steps, you should be able to identify and resolve the issue related to the P20C2 code