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P1891 Transmission Transfer Case Contact Plate Ground Return Open Circuit

The OBD2 code P1891 indicates that there is an open circuit in the ground return for the contact plate in the transmission transfer case, which can affect the operation of the transfer case and related systems

Definition

The OBD2 code P1891 indicates that there is an open circuit in the ground return for the contact plate in the transmission transfer case, which can affect the operation of the transfer case and related systems

Common causes

  • Damaged wiring or connectors
  • Corroded or loose ground connections
  • Faulty transfer case contact plate
  • Malfunctioning transfer case control module
  • Short circuit in the wiring harness
  • Water intrusion or moisture damage
  • Poor electrical connections

Common misdiagnoses

  • Faulty transfer case control module
  • Defective transfer case motor
  • Wiring harness issues
  • Bad ground connections
  • Transmission control module failure
  • Incorrect fluid levels or type
  • Faulty speed sensors
  • Malfunctioning shift linkage
  • Transmission fluid contamination
  • Other electrical issues in the vehicle's 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 Wiring and Connectors

    Visual Inspection: Check the wiring harness and connectors related to the transfer case for any signs of damage, corrosion, or loose connections

  3. 3. Ground Connections

    Ensure that the ground connections are secure and free of corrosion. A poor ground can lead to open circuit issues

  4. 4. Test the Ground Circuit

    Use a multimeter to test the ground circuit for continuity. Disconnect the battery and then check the resistance between the ground point and the contact plate. There should be minimal resistance

  5. 5. If there is no continuity, trace the wiring back to find the break or fault

  6. 6. Check the Transfer Case Control Module (TCCM)

    If applicable, inspect the TCCM for any faults. This module controls the transfer case and can be a source of issues if malfunctioning

  7. 7. Ensure that the module is receiving power and that all connections are secure

  8. 8. Inspect the Transfer Case Contact Plate

    The contact plate itself may be faulty. Inspect it for wear, damage, or corrosion. If it appears damaged, it may need to be replaced

  9. 9. Test the Transfer Case Actuator

    If your vehicle has an actuator for the transfer case, test it to ensure it is functioning correctly. A malfunctioning actuator can cause issues with the contact plate

  10. 10. Check for Short Circuits

    Inspect the wiring for any signs of short circuits. A short can cause the ground return circuit to open, leading to the P1891 code

  11. 11. Clear Codes and Test Drive

    After performing repairs or adjustments, 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. Seek Professional Help

    If the issue persists after performing these steps, it may be best to consult a professional mechanic or technician who has experience with your specific vehicle make and model. By following these steps, you should be able to identify and resolve the issue related to the P1891 code