Also, what causes a rich code? A Thermostat stuck in the open position can mechanically cause a code P0172, especially in cold climates. The engine wont warm up, preventing it from going into closed loop fuel control. Ignition misfires, like mechanical misfires, cause puffs of oxygen to keep hitting the Oxygen Sensors.
Also to know, what does code po172 mean?
Error Code P0172 is described as Fuel System Too Rich, which basically means bank 1s oxygen sensor has detected a rich condition of fuel. This means theres not enough oxygen in the exhaust from too much fuel being delivered into the air and gas mixture for combusion.
What causes an engine to run too rich?
A faulty fuel pressure regulator will cause the fuel pressure to get too high or too low. This can cause a too rich mixture, you do also want to check the vacuum hose to the fuel pressure regulator to make sure there are no leaks around it.