HomeOBD 2 CodesP0172 - Fuel system too rich-bank 1 (2023)

P0172 – Fuel system too rich-bank 1 (2023)

A P0172 code definition is as follows, fuel system too rich on bank 1 . Read below to find out what code P0172 means, symptoms, and how this code can be fixed.

What Does A P0172 Code Mean for my vehicle?

The air and fuel are two of the major items required to complete the combustion process, making it essential that the right amount enters the system at the correct time to ensure a successful combustion event. 

The PCM uses various sensors like the oxygen sensors for example to monitor the air fuel mixture. The main job of the oxygen sensors is to monitor the amount of oxygen that is present in the exhaust system of the vehicle.

 It functions by measuring the difference in oxygen levels. Mainly the difference in the exhaust gases that are leaving the engine cylinders and the outside air that we breath. A high voltage reading would indicate a rich fuel mixture.

A diagnostic trouble code of P0172 is triggered directly by the engine bank 1 oxygen sensor. The oxygen sensor alerts the system when the fuel mixture is too rich. Meaning too much fuel in the exhaust system, or fuel system too rich.

When the diagnostic trouble code P0172 is set  the check engine light is also illuminated at the same time. 

There can be numerous reasons for the fuel mixture to change from its normal stoichiometric range of 14.7:1 (air to fuel). Thus, whenever the engine control system receives a higher than average voltage reading (that indicates a rich air-fuel mixture), a code P0172 or P0175 will be set.

A rich condition is caused when there is too much gasoline or not enough air in the mixture.

P0172 sets when fuel system too rich-bank 1 is set, while P0175 will be set when fuel system too rich-bank 2 is detected.

The Most Common Symptoms of P0172

There would be no noticeable changes in the engine performance level in most cases. However, some cases can result in the following performance problems accompanied by a check engine light.

  • Black smoke from the exhaust pipe due to excessively rich fuel mixture
  • The pungent smell of exhaust fumes
  • decrease in fuel economy
  • A reduction in the engine power
  • Lack of power while accelerating
  • Possible engine misfire
  • Hissing sound (possible vacuum leak)

If the system indicates one of the codes, it is essential to dig deeper. Diagnosing a P0172 or P0175 can be tricky. You may have an engine that is running rich or you may have an issue with a sensor that is reading incorrectly. 

Depending on how bad the fuel mixture is you may also notice the engine misfiring and code P0300 may be present as well.

 As the diagnosis requires more detective work, you may need to look beyond the sensors in the engine computer. 

Why This Code May Appear?

While identifying the primary cause of either a P0172 or P0175 can be tricky. You may need first to rule out minor possible causes of this code and work towards the more difficult to diagnose issues. 

Usually, P0172 or P0175 is due to simple issues, mostly caused by lack of maintenance by the vehicle owner. Remember when looking for causes of this code we are looking for a cause of a rich air-fuel ratio.

Here are some common causes:

  • Insufficient amount of air entering the system. So the first thing you need to do is to check the air filter because a dirty air filter may trigger this code
  • defective fuel pressure regulator 
  • coolant temperature sensor reading incorrectly
  • Leakage in the fuel injectors that can result in allowing too much fuel to enter the combustion chamber.
  • damaged or excessively worn spark plugs
  • improper reading oxygen sensors
  • incorrect reading or damaged Mass Air Flow Sensor (MAF sensor)
  • vacuum line leak (damaged or split hose)
  • incorrectly reading o2 sensor
  • incorrectly reading map sensor

How to Fix the P0172 Code?

After successfully identifying what is causing the P0172 code, or simultaneous codes of P0172 and P0175, you need to figure out how to repair the fault.

Like other codes there are a few possible solutions that you can take the time to check yourself, no matter what your vehicle repair skills. Make sure you check the air filter to ensure it is not excessively dirty, if you have any question make sure you install a new air filter.

It is always a good idea to take the time to use fuel injector cleaner in your fuel tank. If you have a sticky injector that is not closing, fuel injector could possible clean the varnish that is causing the concern.

The use of fuel injector cleaner does not generally repair a problem but use of it overtime will ensure that this varnish does not build up in your fuel system components.

Todays modern fuels also contain excellent fuel additives that ensure that your fuel system is clean and these harmful varnishes do not build up and create possible issues with your vehicle.

Not sure what a fuel pump or fuel injector is, take a look at these great guides that we have created to help you understand how these complicated systems function. The Ultimate Guide to Fuel Injectors and The Ultimate Guide to Fuel Pumps.

 It is usually advised to consult a properly licensed mechanic that can help you repair the code, and even confirm that your diagnosis was correct before wasting your money on an incorrect repair.

A few of the noticeable fixes include:

  •         Repairing leaking vacuum lines
  •         Replacing the faulty fuel injector or the fuel pump
  •         Replacing the coolant temperature sensor or the thermostat.
  •         Proper cleaning of the oxygen and airflow sensors

How Serious Is Code P0172? 

The P0172 code can impose serious environmental issues due to the possible release of black smoke from the tailpipe. These unburned hydrocarbons are considered an extremely harmful pollutant for the environment. 

While it’s okay to drive your vehicle with this code for a short period, an extension of the period can lead to a possible failure of the catalytic convertor.

Estimated Repair Cost

Since there are numerous reasons attached to this code, one or more of the repairs listed below might be required. 

For each repair, the estimated cost, including labor and associated parts, is mentioned.

  •         Cleaning the MAF $100
  •         Repairing the air filter $20
  •         Fuel pressure regulator $200-$350
  •         Repairing the engine coolant temperature sensor $150-$200
  •         A new thermostat $200-$300

Codes Similar To the P0172 Trouble Code

The diagnostic trouble code of P0175 is pretty similar to this one as it also indicates a rich fuel system on bank 2. While diagnosing the P0172, you may also come across other related DTCs, including P0170, P0173, and P0104.

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