P0172 Trouble Code: Meaning, Symptoms, Causes (&Fixing Cost)

The proper supply of air and fuel is very important for the proper working of the engine. Your vehicle engine maintains a proper ratio of air and fuel in the air-fuel mixture. The rich condition occurs when there is too much fuel or insufficient air in the air-fuel mixture. When your vehicle powertrain control module monitors a rich condition, it triggers a trouble code P0172. This article explains the P0172 code symptoms, causes, and fixing cost.

P0172 Code Definition

The P0172 code stands for “Fuel System Too Rich (Bank 1)”. 

Bank 1 represents the side of the engine that contains cylinder no. 1. The O2 sensor measures the amount of air in the exhaust gases that are in the engine cylinder.

What Does the P0172 Code Mean?

The P0172 code indicates that your powertrain control module (PCM) detects too much fuel (or too little air) in the engine cylinder’s air-fuel mixture.

The P0172 code is triggered when your PCM detects a rich running condition on the engine’s Bank 1.

P0172 code

A rich running condition occurs when your vehicle’s air-fuel mixture has too much fuel and insufficient air.

Internal combustion engines run most efficiently when they maintain an air-fuel mixture ratio of 14.7:1.

Insufficient fuel or too much air forces the engine to run lean due to that, your vehicle computer triggers the P0171 or P0174 trouble code. However, insufficient air or too much fuel in the air-fuel mixture forces the engine to run rich, and your vehicle computer triggers the P0172 or P0175 code to alert the driver.

Your PCM contains multiple sensors, including O2 sensors, manifold absolute sensors, and MAF sensors to measure the air-fuel ratio of the engine.

To ensure the efficient working of your vehicle, your PCM also assists in compensating for the lean condition by injecting more fuel into the mixture in an effort to maintain the proper 14.7:1 ratio.

 Causes of P0172 Code

  • Bad fuel pressure regulator
  • Exhaust leaks
  • Faulty fuel pump
  • Faulty spark plug
  • Faulty oxygen sensor at Bank 1
  • Damaged or clogged fuel filters
  • Clogged or faulty fuel injectors
  • A vacuum leak
  • A bad fuel system
  • Faulty MAF sensor
  • Leaky or clogged fuel rails
  • A leaky PCV valve
  • Faulty air-fuel ratio sensor
  • Insufficient fuel
  • Bad PCM

Symptoms of P0172 Code

  • Check engine light is flashing
  • Soot accumulation on spark plug diode
  • Engine misfiring
  • A reduction in the engine power
  • Rough idling
  • Engine stalling
  • Fuel smell from the exhaust
  • Hard to start the vehicle
  • Higher fuel consumption than usual

Read More: P0171 Code Symptoms and Causes

How to diagnose the P0172 Code

To fix the P0172, you need the following tools:

  • OBD-II scanner
  • Basic hand tools
  • Service manual

Follow the below-given steps to fix the P0172 trouble code:

  • Use an OBD-II scan tool to confirm the presence of the P0172 code. Clear the powertrain control module memory to remove the saved codes. Perform a test drive to see what comes back.
  • Inspect the fuel pressure sensor and fuel injectors for damage or blockage
  • Check the fuel pressure. Your vehicle’s fuel pressure must be according to the specifications of the manufacturer.
  • Inspect the fuel system for a damage
  • Inspect the exhaust system for a leak
  • Check the fuel level in the fuel tank.
  • Properly inspect the fuel rails for blockage or leakage
  • Properly inspect the O2 sensors
  • Inspect the MAF sensor and PCV valve for damage
  • Inspect the PCM and replace it if needed

Common P0172 Code Diagnosis Mistakes

  • Not inspecting the connections and wiring before replacing an engine sensor
  • Replacing the unnecessary parts
  • Not clearing the PCM memory after fixing the codes
  • Using the wrong tools to inspect the defective parts
  • Not inspecting the coolant temperature sensor and cooling system
  • Not following the manufacturer’s exact testing procedure step-by-step to avoid misdiagnosis and proper component replacement.

What repairs can fix the P0172 Code?

  • Replacing the bad mass airflow sensor
  • Repairing or replacing the damaged gas cap
  • Cleaning the clogged fuel rails
  • Replacing the faulty fuel pump
  • Cleaning the EGR system
  • Fixing the exhaust leaks
  • Replacing the faulty oxygen sensors
  • Repairing the vacuum leaks
  • Repairing the leaky fuel tank
  • Replacing the bad PCV valve
  • Inspect the fuel level and add more fuel if needed
  • Replacing the faulty fuel injector
  • Replacing the bad fuel pressure sensor
  • Replacing the bad PCM

P0172 Code Fixing Cost

To fix the P0172 code, you need one or more of the below-given repairs:

PartsRepair Cost
Spark plug replacement$180 to $270
O2 sensor replacement$320 to $410 
MAF sensor replacement$100 to $320
Fuel Pump replacement$220 to $1,090
Fuel pressure regulator replacement$280 to $480
Exhaust gas leak repair$120 to $300
MAF sensor cleaning$80 to $110

FAQ Section

How serious is the P0172 code?

The P0172 code is not a much serious trouble code. However, you shouldn’t drive your vehicle with this code for a long time. Driving with code, your vehicle can’t pass the emission test. If the rich air-fuel mixture is burning in your car engine, black smog may come out of the exhaust, which is very dangerous for the atmosphere.

Can I drive with a PO172 Code?

Yes, you can drive with the P0172 code, but you should only drive for a short period of time. Driving with this code may create different problems even in the short term. When your vehicle engine is running rich, you may face poor fuel economy, poor acceleration, or rough idling issues.  However, driving with a rich condition for a long period of time may cause to damage your catalytic converter. Therefore, you shouldn’t drive with this code.

What causes code P0172 in a Chevy?

  • Bad fuel pressure regulator
  • Insufficient fuel
  • Exhaust leaks
  • Faulty spark plug
  • Faulty oxygen sensor at Bank 1
  • Damaged or clogged fuel filters
  • Leaky or clogged fuel rails
  • Clogged or faulty fuel injectors
  • A vacuum leak
  • Faulty MAF sensor
  • A leaky PCV valve
  • Faulty fuel pump
  • Faulty air-fuel ratio sensor
  • A bad fuel system
  • Bad PCM

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