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P1901 TSS Circuit Intermittent Malfunction

The OBD2 code P1901 indicates an intermittent malfunction in the Transmission Speed Sensor (TSS) circuit, which can affect the transmission's ability to function properly

Definition

The OBD2 code P1901 indicates an intermittent malfunction in the Transmission Speed Sensor (TSS) circuit, which can affect the transmission's ability to function properly

Common causes

  • Faulty Transmission Control Module (TCM)
  • Damaged wiring or connectors in the TSS circuit
  • Faulty Transmission Speed Sensor (TSS)
  • Poor electrical connections
  • Corroded terminals
  • Internal transmission issues
  • Software glitches in the TCM
  • Low transmission fluid levels or contamination

Common misdiagnoses

  • Transmission control module (TCM) failure
  • Faulty speed sensors
  • Wiring issues or shorts in the harness
  • Incorrect fluid levels or quality
  • Faulty transmission solenoids
  • Engine control module (ECM) issues
  • Mechanical transmission problems
  • Poor electrical connections or corrosion

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 other issues present

  2. 2. Inspect Wiring and Connectors

  3. 3. Visually inspect the wiring and connectors associated with the TSS. Look for signs of damage, corrosion, or loose connections

  4. 4. Ensure that the connectors are securely attached and that there are no bent pins

  5. 5. Test the TSS

  6. 6. Use a multimeter to test the resistance and voltage output of the TSS. Compare your readings to the specifications provided in the vehicle’s service manual

  7. 7. If the sensor is faulty, it may need to be replaced

  8. 8. Check the TCM

  9. 9. Inspect the Transmission Control Module for any signs of damage or corrosion

  10. 10. Ensure that the TCM is receiving the correct input signals from the TSS

  11. 11. Inspect the Transmission Fluid

  12. 12. Check the transmission fluid level and condition. Low or dirty fluid can affect sensor performance

  13. 13. If the fluid is contaminated, consider performing a transmission fluid change

  14. 14. Look for Intermittent Issues

  15. 15. Since the code indicates an intermittent malfunction, pay attention to the conditions under which the code appears. It may be related to temperature, load, or specific driving conditions

  16. 16. Test drive the vehicle to see if you can replicate the issue

  17. 17. Check for Ground Issues

  18. 18. Ensure that the ground connections for the TSS and TCM are secure and free of corrosion. Poor grounding can lead to intermittent issues

  19. 19. Scan for Software Updates

  20. 20. Check if there are any software updates available for the TCM. Sometimes, manufacturers release updates to address known issues

  21. 21. Clear Codes and Test Drive

  22. 22. After performing any repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the code returns

  23. 23. Consult a Professional

  24. 24. If the issue persists after following these steps, it may be necessary to consult a professional mechanic or technician who has experience with transmission systems and OBD-II diagnostics. By following these steps, you can systematically diagnose and address the P1901 code. Always refer to the specific service manual for your vehicle for detailed procedures and specifications