WOMS
P code powertrain Medium severity

P0728 Engine Speed Input Circuit Intermittent

The OBD2 code P0728 indicates that there is an intermittent issue with the engine speed input circuit, which may affect the transmission's ability to function properly

Definition

The OBD2 code P0728 indicates that there is an intermittent issue with the engine speed input circuit, which may affect the transmission's ability to function properly

Common causes

  • Faulty engine speed sensor
  • Damaged wiring or connectors
  • Poor electrical connections
  • Faulty transmission control module (TCM)
  • Faulty powertrain control module (PCM)
  • Intermittent signal from the engine speed sensor
  • Mechanical issues in the transmission
  • Corroded or damaged sensor terminals

Common misdiagnoses

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Bad vehicle speed sensor (VSS)
  • Wiring issues or shorts in the engine speed input circuit
  • Faulty crankshaft position sensor
  • Faulty camshaft position sensor
  • Transmission issues or failures
  • Incorrectly installed or damaged connectors
  • Faulty ignition system components
  • Software issues or updates needed in the ECM/TCM

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context and help identify related issues

  2. 2. Inspect Wiring and Connectors

  3. 3. Visually inspect the wiring and connectors associated with the engine speed sensor and the transmission control module. Look for signs of damage, corrosion, or loose connections

  4. 4. Ensure that all connectors are securely plugged in and that there are no broken wires

  5. 5. Test the Engine Speed Sensor

  6. 6. Locate the engine speed sensor (often found on or near the transmission)

  7. 7. Use a multimeter to test the sensor's resistance and output voltage according to the manufacturer's specifications. If the readings are outside the specified range, the sensor may need to be replaced

  8. 8. Check the Power and Ground

  9. 9. Verify that the engine speed sensor is receiving the correct voltage and has a good ground connection. Use a multimeter to check for power at the sensor connector while the ignition is on

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

  11. 11. If the sensor and wiring are in good condition, the issue may lie with the TCM. Check for any signs of damage or corrosion

  12. 12. If possible, perform a reset or reprogramming of the TCM, as it may have stored erroneous data

  13. 13. Look for Mechanical Issues

  14. 14. Inspect the transmission for any mechanical issues that could affect the operation of the speed sensor, such as low fluid levels or internal damage

  15. 15. Clear the Codes and Test Drive

  16. 16. After performing the necessary repairs or replacements, clear the trouble codes using the OBD-II scanner

  17. 17. Take the vehicle for a test drive to see if the code reappears. Monitor the vehicle's performance to ensure that the issue has been resolved

  18. 18. Consult a Professional

  19. 19. If the problem persists after following these steps, it may be necessary to consult a professional mechanic or technician who has access to specialized diagnostic equipment and experience with your specific vehicle make and model. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P0728 code