WOMS
P code powertrain Medium severity

P071B Transmission Mode Switch "A" Circuit Low

The OBD2 code P071B indicates a low voltage condition in the Transmission Mode Switch "A" circuit, which may affect the transmission's ability to select the correct mode or gear

Definition

The OBD2 code P071B indicates a low voltage condition in the Transmission Mode Switch "A" circuit, which may affect the transmission's ability to select the correct mode or gear

Common causes

  • Faulty transmission mode switch
  • Wiring issues (shorts or open circuits)
  • Poor electrical connections
  • Corroded connectors
  • Faulty transmission control module (TCM)
  • Low transmission fluid levels
  • Internal transmission issues

Common misdiagnoses

  • Faulty transmission control module (TCM)
  • Defective transmission range sensor
  • Wiring issues or shorts in the circuit
  • Faulty transmission fluid temperature sensor
  • Malfunctioning gear shift lever assembly
  • Incorrectly installed or damaged transmission components
  • Software issues or outdated firmware in the TCM

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 Transmission Mode Switch

    Locate the transmission mode switch (also known as the gear selector switch) and visually inspect it for any signs of damage, corrosion, or loose connections

  3. 3. Ensure that the switch is properly mounted and that there are no broken wires

  4. 4. Test the Wiring and Connectors

    Check the wiring harness and connectors associated with the transmission mode switch for any signs of wear, fraying, or corrosion

  5. 5. Use a multimeter to test the continuity of the wires. Look for any breaks or shorts in the circuit

  6. 6. Check Voltage and Ground

    With the ignition on (engine off), use a multimeter to check the voltage at the transmission mode switch connector. Compare the readings to the specifications in the vehicle’s service manual

  7. 7. Ensure that the ground connection is solid and that there is no voltage drop

  8. 8. Test the Transmission Mode Switch

    If the switch appears to be faulty, you can test it using a multimeter. Check for proper resistance values when the switch is in different positions

  9. 9. If the switch is defective, it may need to be replaced

  10. 10. Inspect the Transmission Control Module (TCM)

    If the switch and wiring are in good condition, the issue may lie with the Transmission Control Module. Check for any software updates or known issues with the TCM for your specific vehicle model

  11. 11. Clear the 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 reappears. Monitor the transmission operation to ensure it is functioning correctly

  13. 13. Consult a Professional

    If the issue persists after performing these steps, it may be best to consult a professional mechanic or technician who has experience with transmission issues and can perform more advanced diagnostics.Additional Tips: - Always refer to the vehicle’s service manual for specific diagnostic procedures and specifications. - Ensure that you are working in a safe environment and take necessary precautions when working on the vehicle. By following these troubleshooting steps, you should be able to identify the cause of the P071B code and take appropriate action to resolve the issue