WOMS
P code powertrain Medium severity

P202B Reductant Tank Heater Control Circuit Low

The OBD2 code P202B indicates a low voltage or malfunction in the reductant tank heater control circuit, which is responsible for heating the diesel exhaust fluid (DEF) in the tank to prevent freezing

Definition

The OBD2 code P202B indicates a low voltage or malfunction in the reductant tank heater control circuit, which is responsible for heating the diesel exhaust fluid (DEF) in the tank to prevent freezing

Common causes

  • Faulty reductant tank heater
  • Open or shorted wiring in the heater circuit
  • Bad connector or corroded terminals
  • Failed power supply to the heater
  • Faulty engine control module (ECM)
  • Poor ground connection
  • Blown fuse related to the reductant tank heater circuit

Common misdiagnoses

  • Faulty reductant tank heater
  • Wiring issues or shorts in the circuit
  • Defective engine control module (ECM)
  • Faulty temperature sensor
  • Issues with the reductant pump
  • Low reductant fluid 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 Tank Heater

    Visual Inspection: Check the reductant tank heater for any visible damage, corrosion, or loose connections

  3. 3. Wiring and Connectors

    Inspect the wiring harness and connectors for signs of wear, fraying, or corrosion. Ensure all connections are secure

  4. 4. Test the Reductant Tank Heater

    Resistance Test: Use a multimeter to measure the resistance of the reductant tank heater. Compare the reading to the manufacturer's specifications. A reading that is too high or too low may indicate a faulty heater

  5. 5. Power Supply

    Check if the heater is receiving the correct voltage when activated. If not, there may be an issue with the power supply or control circuit

  6. 6. Check the Control Circuit

    Fuses and Relays: Inspect the fuses and relays associated with the reductant tank heater circuit. Replace any blown fuses or faulty relays

  7. 7. Control Module

    If the heater and wiring are in good condition, the issue may lie with the engine control module (ECM) or the module that controls the SCR system. Check for software updates or faults in the module

  8. 8. Inspect the Reductant Fluid

    Ensure that the reductant fluid (urea) is at the proper level and is not contaminated. Low or contaminated fluid can affect the operation of the heater

  9. 9. Check for Ground Issues

    Ensure that the ground connections for the reductant tank heater circuit are clean and secure. Poor grounding can lead to low voltage readings

  10. 10. Clear Codes and Test Drive

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

  11. 11. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the P202B code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues

  12. 12. Professional Diagnosis

    If the issue persists after performing these steps, consider seeking help from a professional mechanic or dealership. They may have specialized diagnostic tools and experience with your vehicle's specific system. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P202B code