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P1791 TP (Electric) Circuit Malfunction

The OBD2 code P1791 indicates a malfunction in the throttle position (TP) electric circuit, which can affect the engine's performance and response to acceleration

Definition

The OBD2 code P1791 indicates a malfunction in the throttle position (TP) electric circuit, which can affect the engine's performance and response to acceleration

Common causes

  • Faulty throttle position sensor (TPS)
  • Wiring issues or damaged connectors
  • Malfunctioning electronic throttle control (ETC) system
  • Failed engine control module (ECM)
  • Poor ground connections
  • Software issues or calibration errors
  • Intermittent electrical faults
  • Faulty accelerator pedal position sensor

Common misdiagnoses

  • Throttle Position Sensor (TPS) failure
  • Wiring issues or shorts in the circuit
  • Engine Control Module (ECM) malfunction
  • Accelerator pedal position sensor issues
  • Transmission control module (TCM) problems
  • Faulty connectors or terminals
  • Software or calibration issues in the ECM/TCM
  • Vacuum leaks affecting throttle response

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context for the issue

  2. 2. Inspect Wiring and Connectors

  3. 3. Visually inspect the wiring and connectors associated with the throttle position sensor (TPS) and the electronic throttle control system. Look for signs of damage, corrosion, or loose connections

  4. 4. Ensure that all connectors are securely attached and free of dirt or moisture

  5. 5. Test the Throttle Position Sensor

  6. 6. Use a multimeter to test the TPS. Check the resistance and voltage output according to the manufacturer's specifications

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

  8. 8. Check the Throttle Body

  9. 9. Inspect the throttle body for any signs of carbon buildup or physical damage. Clean the throttle body if necessary, as dirt can affect the operation of the throttle position sensor

  10. 10. Ensure that the throttle plate moves freely and is not sticking

  11. 11. Inspect the Electronic Control Module (ECM)

  12. 12. Check for any software updates or reprogramming that may be required for the ECM. Sometimes, a simple update can resolve communication issues

  13. 13. If the ECM is suspected to be faulty, further testing may be required

  14. 14. Check for Ground Issues

  15. 15. Ensure that the ground connections for the throttle position sensor and related components are secure and free of corrosion

  16. 16. Test the Accelerator Pedal Position Sensor

  17. 17. If applicable, check the accelerator pedal position sensor, as it works in conjunction with the throttle position sensor. Test its output and wiring

  18. 18. Clear Codes and Test Drive

  19. 19. After performing the necessary 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

  20. 20. Refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the throttle position circuit

  21. 21. Seek Professional Help

  22. 22. If the issue persists after performing these steps, it may be best to consult a professional mechanic or technician who has experience with electronic throttle control systems. By following these troubleshooting steps, you can systematically identify and resolve the issue related to the P1791 code