How to fix P0172 Code: Fuel System Too Rich (Bank 1)
A Rich condition exists if the engine is getting more gas than air into the cylinders. (Air/Fuel Ratio is off.
(How a P0172 Code is triggered.) The oxygen sensor is reading the amount of oxygen burnt off during combustion and is reporting the information to the computer. The sensor is reading there is more oxygen than should be on Bank1 side of the engine.
P0172 Code can be problematic to fix since it can be caused by several things.

Possible Causes of a P0172 Code:
Oxygen Sensor (Bank 1 Sensor 1)
Bad Fuel Injector
Vacuum Leak

Other Possible Causes but Usually Would also Cause Bank2 Issues (P0175 Code: Engine Too Rich Bank 2)
Bad Mass Air Flow Sensor or Other Sensor
Blocked Air Intake
Bad Fuel Pressure Regulator or Fuel Pump

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