WOMS
P code powertrain Medium severity

P20C7 Reductant Heater "D" Control Circuit Low

The OBD2 code P20C7 indicates a low voltage or malfunction in the control circuit for the reductant heater "D," which is part of the diesel exhaust fluid (DEF) system used to reduce emissions

Definition

The OBD2 code P20C7 indicates a low voltage or malfunction in the control circuit for the reductant heater "D," which is part of the diesel exhaust fluid (DEF) system used to reduce emissions

Common causes

  • Faulty reductant heater "D"
  • Open circuit in the heater wiring
  • Short circuit in the heater wiring
  • Poor electrical connections or corroded terminals
  • Faulty power supply to the heater
  • Malfunctioning engine control module (ECM)
  • Blown fuse related to the reductant heater circuit

Common misdiagnoses

  • Faulty reductant heater
  • Wiring issues or shorts in the circuit
  • Defective engine control module (ECM)
  • Low DEF (diesel exhaust fluid) level
  • Faulty temperature sensor
  • Issues with the DEF injector
  • 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 Wiring and Connectors

    Visually inspect the wiring and connectors associated with the reductant heater "D" circuit. Look for signs of damage, corrosion, or loose connections

  3. 3. Ensure that all connectors are securely attached and free of dirt or moisture

  4. 4. Test the Reductant Heater

    If accessible, test the reductant heater itself for continuity using a multimeter. Check the resistance of the heater element; it should be within the manufacturer's specified range

  5. 5. If the heater is open or shorted, it may need to be replaced

  6. 6. Check the Control Circuit

    Use a multimeter to check the voltage at the control circuit. Ensure that the voltage is within the expected range when the vehicle is running

  7. 7. If the voltage is low, trace the circuit back to the power source and check for any breaks or shorts

  8. 8. Inspect the Fuse

    Check the fuse associated with the reductant heater circuit. If the fuse is blown, replace it and see if the code returns

  9. 9. Examine the Engine Control Module (ECM)

    If all other components check out, there may be an issue with the ECM. Ensure that the ECM is functioning properly and that it is sending the correct signals to the reductant heater

  10. 10. Check for any software updates or reprogramming that may be required

  11. 11. Clear the Codes and Test Drive

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

  12. 12. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the P20C7 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues that could assist in troubleshooting

  13. 13. Seek Professional Help

    If you are unable to resolve the issue after these steps, consider seeking help from a qualified mechanic or dealership, as they may have specialized tools and knowledge to diagnose the problem further. By following these steps, you should be able to identify and resolve the issue related to the P20C7 code. Always refer to the vehicle's service manual for specific procedures and specifications