We don't have a clue as to which code set or why but they never say to replace parts. That's what too many people believe. Codes only indicate which circuit or system needs further diagnosis. If someone replaced a part, often a sensor, in response to a code and expected that to take care of the Check Engine light, there's only a 50 percent chance the new part would solve the problem.
Also, once a problem is repaired the fault code(s) have to be erased or the light may come back on. That usually happens when the problem was somewhat serious. On most cars if an intermittent problem no longer reoccurs, (or a repaired serious problem no longer occurs, the fault code will erase automatically after certain conditions are met, commonly 50 engine starts without that problem showing up again.