The P0172 Code and How To Deal With It!

Fuel and air are very critical for the internal combustion process. Thus, for a successful ignition, a proper amount of fuel and air must enter the internal combustion chamber. If not, your engine might under perform or use too much fuel. 

The ECU (engine control unit) typically controls the flow of fuel and air into the combustion chamber. It is the essential computer responsible for virtually managing every internal function of your vehicle, such as the amount of fuel going into the combustion chamber. 

However, if the ECU malfunctions or the fuel injection system /  o2 sensors experiences some problems, it may lead to the engine receiving more fuel than what it requires to maintain your vehicle’s power demands. Therefore, this makes the ECU to set the trouble code P0172.

The right air-to-fuel ratio is about 14.7:1 since this ratio leads to fuel economy and can optimize engine power. Power-train module (PCM) includes ECU, and for this reason, it may lead to code P0172. Fortunately, a supplier like will help you resolve PCM issues.

Although P0172 might not likely lead to drivability issues, it can cause misfire. Other symptoms include:

• Rough idling

• Engine hesitating

• Poor fuel economy

• Deficiency of power on acceleration

• Blinking MIL / Check Engine Light

Flagship one LOGO p0172 code

What Does System Too Rich Bank 1 mean?

System too rich bank 1 means that the oxygen sensor in bank 1 identified a rich situation (presence of inadequate amount of oxygen in the exhaust). The engine control unit constantly monitors and communicates with different sensors of the fuel injection system / fuel trim .

Several instruments and sensors can help detect the amount of fuel in the combustion compartment. They are the mass air flow sensor, oxygen sensors, and manifold absolute pressure.

For instance, the oxygen sensor measures the amount of oxygen in your exhaust gases in cylinder 1 (bank 1). If it detects the presence of very little oxygen, it shows that the ratio of air-fuel is not where it should be. The detection of too much fuel mean that there is insufficient oxygen. Bank 1 is technically cylinder 1, which is the area of the vehicle’s engine with the first cylinder. 

p0172 code Shop at flagship one inc for engine control module

How do I fix P0172 too rich?

P0172 code is a serious condition that can lead to black smog, which is an environment pollutant. Also, your car might not pass the state vehicle inspection. Here are ways to fix P0172 code fuel too rich:

• Cleaning the mass air flow sensor and oxygen sensors.

• Replacing the spark plugs.

• Replacing the coolant temperature sensor or thermostat.

• Repairing your vacuum leaks.

• Replacing a damaged fuel regulator, fuel pump, or fuel injector.

• Replacing a restricted air filter.

Can bad spark plugs cause P0172?

Yes, bad spark plugs can cause p0172. Spark plugs are amongst the key compartments of a vehicle’s ignition system. They are responsible for providing the essential spark for ignition to give the engine the needed power to proper down the road. 

With time, spark plugs’ electrodes wear out and may lead to performance issues. Such inefficiencies can increase the supply of fuel into the engine. Thus, it causes a rich condition, which leads to p0172.  

There are many causes of code P0172, and they are:

• Faulty oxygen sensor

• Dirty MAF (mass air flow) sensor

• Damaged fuel line

• Defective fuel pressure regulator
• Damaged/stuck open thermostat

• Faulty spark plugs

• Clogged/dirty air filter 

• Defective fuel injectors that leak fuel into your combustion chamber
• Faulty MAP (manifold absolute pressure) sensor

• Damaged throttle position sensor

Because of the many causes of code P072, its diagnosis and fixing might be challenging. It is prudent to start with the easiest alternatives, such as checking and cleaning the air filter and mass air flow sensor, then proceed to the cheapest and easiest potential causes. 

Nonetheless, here are some of the ways you can fix code P0172:

• Check your fuel pressure to ensure that is within the right range. Typically, excess pressure because of a pinched return line or faulty pressure might lead to more fuel entering the combustion chamber than what the ECU expects. 

• MAF contamination might skew the measuring of the air going into the combustion compartment. Thus, it leads to inaccurate fuel injection calculations. It is advisable to clean your MAF to solve this issue. For a more lasting resolution, you can replace MAF, use a new air filter, and ensure to properly seal the air box. 

• Check proper IAT (intake air temperature) and ECT readings. It is a vital resolution process since the ECU might not pick up on some stuck sensors. Also, make sure that the IAT and ECT readings are in standard ranges.

• Inspect the fuel lines for possible pinches, leaks and cracks. 

If you detect only P0172, it is possible that concurrent bank 1 diagnostic trouble codes like a cylinder misfire occurred. Therefore, shift your attention to bank 1 as follows:

• Exhaust – check your exhaust for possible leaks, especially between the oxygen sensor and cylinder head. The exhaust pressure pulses can create a partial vacuum, which might allow the passage of air. Atmospheric oxygen going into the combustion chamber before the H02S might skew the measurements of oxygen. 

• Cylinder misfire might dump the unburnt fuel into your exhaust stream. Thus, before diagnosing a rich condition, it is wise to check and repair a cylinder misfire. Ensure to focus of DTCs like those relating to the ignition system or variable valve timing (VVT).

• Fuel pressure drop – record fuel pressure while the engine is running and shut it off. The fuel pressure might drop a little. However, it should remain constant for at least 10-15 minutes. If it continues to drop, then your fuel injector might be leaking, and this can lead to a rich situation as well as possible misfire situation.


The right amount of fuel and air entering the engine is essential since it ensures fuel economy and optimizes engine power. Thus, it saves you money and other issues that may come with system too rich bank 1. There are some ways easy ways that you can do to solve this problem and check engine light. However, if you are not sure about the diagnosis, seek assistance from your mechanic. It helps prevent more issues that arise from misdiagnosis. 

Leave a Reply

Your email address will not be published.