WOMS
P code powertrain High severity

P0173 Fuel Trim Malfunction (Bank 2)

The OBD2 code P0173 indicates that there is a fuel trim malfunction on bank 2 of the engine, meaning the engine control module is unable to maintain the correct air-fuel mixture for that bank, potentially leading to...

Definition

The OBD2 code P0173 indicates that there is a fuel trim malfunction on bank 2 of the engine, meaning the engine control module is unable to maintain the correct air-fuel mixture for that bank, potentially leading to poor engine performance and increased emissions

Common causes

  • Vacuum leaks
  • Faulty fuel injectors
  • Faulty mass air flow (MAF) sensor
  • Faulty oxygen sensor
  • Fuel pressure issues
  • Exhaust leaks
  • Engine control module (ECM) issues
  • Dirty or clogged air filter
  • Faulty fuel pump
  • Incorrect fuel type or quality

Common misdiagnoses

  • Faulty oxygen sensor
  • Vacuum leaks
  • Mass air flow (MAF) sensor issues
  • Fuel injector problems
  • Exhaust leaks
  • Fuel pressure regulator failure
  • Engine coolant temperature sensor malfunction
  • Intake air temperature sensor issues
  • EGR system problems
  • PCM (Powertrain Control Module) issues

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. Codes related to fuel delivery, air intake, or sensors can provide additional context

  2. 2. Inspect Fuel Trim Data

    Monitor the fuel trim data using a scan tool. Look at both short-term and long-term fuel trim values for Bank 2. If the values are significantly positive or negative, it indicates a fuel delivery issue

  3. 3. Visual Inspection

    Inspect the engine for any obvious signs of issues

  4. 4. Check for vacuum leaks around intake manifold gaskets, vacuum hoses, and throttle body

  5. 5. Look for any damaged or disconnected hoses

  6. 6. Inspect the fuel injectors for leaks or clogs

  7. 7. Check Fuel Pressure

    Use a fuel pressure gauge to check the fuel pressure. Ensure it meets the manufacturer’s specifications. Low fuel pressure can cause lean conditions, while high pressure can cause rich conditions

  8. 8. Inspect the Mass Air Flow (MAF) Sensor

    A faulty MAF sensor can lead to incorrect air-fuel mixture readings. Clean or replace the MAF sensor if necessary

  9. 9. Check Oxygen Sensors

    Inspect the oxygen sensors, especially the one upstream of the catalytic converter on Bank 2. A malfunctioning sensor can provide incorrect feedback to the ECM, affecting fuel trim

  10. 10. Examine the Engine Coolant Temperature (ECT) Sensor

    A faulty ECT sensor can cause the engine to run rich or lean. Check the sensor and its wiring for proper operation

  11. 11. Inspect the Throttle Position Sensor (TPS)

    Ensure the TPS is functioning correctly. A malfunctioning TPS can affect fuel delivery and air-fuel mixture

  12. 12. Check for Exhaust Leaks

    Inspect the exhaust system for leaks, especially before the oxygen sensors. Exhaust leaks can skew sensor readings

  13. 13. Review Fuel Quality

    Ensure that the fuel being used is of good quality and free from contaminants. Poor fuel can affect combustion and fuel trim.1

  14. 14. Perform a Smoke Test

    If vacuum leaks are suspected, perform a smoke test to identify any leaks in the intake system.1

  15. 15. Check for Software Updates

    Sometimes, manufacturers release software updates for the ECM that can resolve known issues. Check for any available updates.1

  16. 16. Clear Codes and Test Drive

    After performing repairs, clear the codes and take the vehicle for a test drive to see if the code returns.1

  17. 17. Consult a Professional

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic for further diagnosis. By following these troubleshooting steps, you can systematically identify and resolve the underlying issues causing the P0173 code