The Code Reader takes common DTCs, breaks down when and why they occur and looks at symptoms and causes to help listeners make an accurate diagnosis.
P0172 has the same relevancy as P0175, which is “system too rich, bank 2.” The only difference is that a vehicle with an inline engine will only indicate P0172, and if the engine is a V- or opposed configuration, it can indicate either code, or both at the same time, depending on the cause of the problem.
When this code is stored, it means that the control unit has recognized through the readings from the oxygen or air/fuel ratio sensors that there is a lack of oxygen in the exhaust, representing too much fuel in the combustion process. The control unit is adjusting for the rich condition by removing or reducing the amount of fuel delivery to the cylinders.
When the control unit has to adjust for this condition for too long, it sets this code to alert you of the problem.