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P0173 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


A problem with the fuel trim system in Bank 2 of the engine is referred to in the P0173 DTC code. Specifically, it indicates that the engine control module (ECM) or powertrain control module (PCM) has detected a fuel trim that is too high. Bank 2 typically refers to the side of the engine opposite the side of cylinder 1.


When code P0173 is activated, it indicates that the fuel mixture on Bank 2 of the engine is too high compared to the quantity of air being supplied; this means there’s an overabundance of fuel. The result is a reduction in fuel efficiency and an increase in emissions.


The P0173 DTC code may appear as a result of several factors:

  • Faulty Oxygen Sensor: A malfunctioning oxygen sensor may not accurately measure the oxygen levels in the exhaust gases, leading to improper fuel trim adjustments.
  • Vacuum Leaks: Unmetered air entering the engine as a result of vacuum leaks might result in an excessively rich fuel mixture.
  • A malfunctioning Mass Air Flow (MAF) Sensor: The fuel trim may be impacted if the MAF sensor reports inaccurate information about the incoming air.
  • Fuel System Issues: The correct fuel-air combination might be hampered by issues with the fuel injectors, fuel pressure regulator, or fuel pump.


The following signs and symptoms might be present when the P0173 DTC code is present:

  • Reduced Fuel Efficiency: Because of the rich air-fuel mixture, the engine may use more fuel than usual.
  • Decreased Fuel Efficiency: The engine may consume more fuel than usual due to the rich air-fuel mixture.
  • Rough Idling: The engine may experience rough idling or hesitation during acceleration.
  • Increased Emissions: The vehicle can fail an emissions test because of emissions that are greater than usual.


The procedures below can be used by a competent mechanic to correctly diagnose the P0173 DTC code:

  • OBD-II Scanner: Using an OBD-II scanner, the mechanic can retrieve the trouble code and other relevant data from the vehicle’s onboard computer.
  • Visual Inspection: A complete visual examination is performed to look for any obvious damage or leaks in the fuel system, intake system, and vacuum lines.
  • Inspect the Oxygen Sensor: check the voltage output of the oxygen sensor to see if it is operating properly.
  • Examine the MAF Sensor: Check the Mass Air Flow (MAF) sensor’s functionality and, if required, clean or replace it.

Common mistakes

Common errors to avoid when working with the P0173 code include:

  • Ignoring Other Codes: P0173 may be accompanied by other relevant codes, and dismissing them might result in a failure to notice important problems.
  • Replacing parts too soon: To prevent wasting money, it’s important to undertake a thorough diagnosis before replacing any components.
  • Ignoring Regular Maintenance: The operation of the fuel trim system can be greatly impacted by neglecting routine maintenance, which includes cleaning or changing air filters.

How serious is this?

Various factors, such as the complexity of the issue and driving conditions, affect the seriousness of the P0173 DTC code. While the vehicle may continue to be in use under this code, prolonged driving with a high mix of air and fuel oil can result in reduced fuel efficiency and possible damage to catalytic converters.

What repairs can fix the code?

repair manuals

The P0173 DTC code can be fixed using the following fixes, depending on the diagnosis:

  • Replacing a defective Oxygen Sensor: If the oxygen sensor is defective, the problem can be fixed by replacing it with a new, functional one.
  • Repairing Vacuum Leaks: Fuel trim can be adjusted by addressing any vacuum leaks in the intake system.
  • Fixing Fuel System Components: Correct fuel trim can be obtained by addressing problems with the fuel injectors, fuel pressure regulator, or fuel pump.

Related codes

Other related DTC codes include P0170 (Fuel Trim Malfunction Bank 1) and P0174 (System Too Lean Bank 2). These codes may provide additional insights into the fuel trim system’s overall performance.


The DTC code P0173 indicates a possible problem with the fuel-cutting system on Bank 2 of the engine. In order to ensure the optimum performance of the engine, fuel efficiency, and emission compliance, timely diagnosis and appropriate repair are essential. If you encounter this code, it is advised to seek professional assistance for a correct diagnosis and resolution of the problem so that your experience driving smoothly can be assured.

P0173 Code – What Does It Mean & How To Fix It