The P0172 fault code is set when the Engine Control Unit detects that there is too much (or not enough) fuel in the air-fuel mix. P0172 is a fault code that is triggered when the Engine Control Unit (ECU/ECM/PCM) detects too much fuel or not enough air in the engine’s air-fuel mixture. To monitor the air-fuel ratio, the ECU makes use of a variety of components such as mass air flow sensors (MAF), oxygen sensors, and the manifold absolute pressur (MAP) sensor. Oxygen sensors measure the amount carbon monoxide and oxygen in exhaust gases to calculate the air-fuel mixture. The optimal air-fuel ratio is 14.7 to 1. It means that 14.7 units of oxygen are required to burn 1 unit fuel in a petrol engine’s combustion chamber. This mixture provides the best power output at the lowest fuel consumption.
The ECU can adjust the ratio of combustion when it becomes rich or lean. If the tolerance is too large, the ECU cannot adjust and will generate the P0172 error code. Rich means that the air-fuel ratio of the engine is too high and there is not enough air. The term “lean” indicates that there is a high oxygen ratio and a low petrol ratio.
This fault code has ‘Bank 1″ in it. It indicates that there is a problem with the cylinder number 1 on the right side of the engine. Four-cylinder cars only have a single row. Six-cylinder engines have two rows with three cylinders in each row. The fault in these vehicles should be found on the side of the vehicle where the 1st cylinder is.
Note: This code is similar to P0175 and may be displayed by the vehicle computer at the same time.
Table of Contents
What are the causes of fault code P0172?
The fault code P0172 may be caused by a variety of problems. In order to determine the cause, it is necessary to examine the critical components that are responsible for ensuring a correct fuel mixture.
- One possible cause is a dirty or faulty Mass Air Flow Sensor.
- Oxygen sensor failure
- Fuel injector leaks can allow too much fuel to enter the combustion chamber
- Fuel regulators that are faulty can’t regulate pressure in the engine.
- A faulty fuel pump
- Vacuum leaks
- Possible faults in the cooling system such as a stuck or faulty thermostat
- Worn spark plugs
- Engine oil that is dirty and hasn’t been changed in a long time
- Air filter clogged
- Air intake restrictions
- Exhaust restriction (clogged exhaust, silencer or catalytic convertor)
- Exhaust leak
What are the symptoms of fault code P0172?
- Engine fault light illuminatingHigh fuel consumption
- Black smoke from exhaust
- Reduced engine performance
- Engine misfiring
- Idling is not allowed
- Hesitation before accelerating
- The smell of raw fuel can be detected in the cabin or exhaust.
How to Fix Fault Code P0172?
- Repair vacuum leaks. Replace faulty fuel injectors
- Fuel pumps that are faulty can be replaced
- Fuel regulator replacement for faulty units
- Replace air filters that are excessively clogged
- Replace a faulty thermostat or coolant temp sensor
- Spark plugs that are faulty can be replaced
- Clean or replace faulty oxygen sensors
- Cleaning or replacement for a faulty mass flow sensor
