Rich air-fuel mixture
A rich code means the trims have been pulling fuel because the mixture looked to contain too much fuel.
P0172 is bank 1 and P0175 is bank 2. A leaking injector, high fuel pressure, a stuck purge valve, or a sensor that reports too little air can push the system rich.
Black smoke or a strong fuel smell can accompany it. Use the DTC page to order the pressure and sensor checks.
A trouble code marks a condition to test. It does not by itself prove which part to replace.