WOMS
P code powertrain Medium severity

P071A Transmission Mode Switch "A" Circuit

The OBD2 code P071A indicates a malfunction in the Transmission Mode Switch "A" circuit, which is responsible for signaling the transmission control module about the selected transmission mode (e.g., drive, reverse,...

Definition

The OBD2 code P071A indicates a malfunction in the Transmission Mode Switch "A" circuit, which is responsible for signaling the transmission control module about the selected transmission mode (e.g., drive, reverse, neutral)

Common causes

  • Faulty transmission mode switch
  • Wiring issues (shorts, opens, or corrosion)
  • Poor electrical connections
  • Faulty transmission control module (TCM)
  • Software issues in the TCM
  • Malfunctioning gear selector assembly
  • Low transmission fluid levels or contamination
  • Internal transmission problems

Common misdiagnoses

  • Faulty transmission control module (TCM)
  • Defective transmission range sensor
  • Wiring issues or shorts in the circuit
  • Malfunctioning transmission solenoids
  • Incorrectly diagnosed engine control module (ECM) issues
  • Problems with the vehicle speed sensor (VSS)
  • Low transmission fluid levels or quality issues
  • Faulty or misaligned gear shift linkage

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

    Visual Inspection: Check the transmission mode switch for any visible damage, corrosion, or loose connections

  3. 3. Wiring and Connectors

    Inspect the wiring harness and connectors for fraying, breaks, or poor connections. Ensure that all connectors are securely attached

  4. 4. Test the Transmission Mode Switch

    Multimeter Testing: Use a multimeter to test the resistance and continuity of the transmission mode switch. Compare the readings to the specifications in the vehicle’s service manual

  5. 5. Functionality Check

    If possible, manually operate the switch to see if it functions correctly and sends the appropriate signals

  6. 6. Check for Short Circuits or Open Circuits

    Use the multimeter to check for shorts to ground or open circuits in the wiring leading to the transmission mode switch. This can help identify wiring issues

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

    Check the TCM for any signs of damage or corrosion. Ensure that it is properly connected and functioning

  8. 8. If you have access to a scan tool, check for any TCM-related codes or issues

  9. 9. Check Power and Ground

    Verify that the transmission mode switch is receiving the correct voltage and ground. Use a multimeter to check for power at the switch when the ignition is on

  10. 10. Look for Mechanical Issues

    Inspect the transmission for any mechanical issues that could affect the operation of the mode switch. This includes checking for proper fluid levels and any signs of internal damage

  11. 11. 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

  12. 12. Seek Professional Help

    If you are unable to resolve the issue after following these steps, it may be best to consult a professional mechanic or technician who has experience with transmission issues. By following these troubleshooting steps, you should be able to identify the cause of the P071A code and take appropriate action to resolve it