Why do you have three codes that all pretty much mean the same thing PO441,PO 442,&PO 446 ?

Question

Why do all three of these codes mean the same thing? Or do they not all mean the same thing?

Answer 1

P0441 Evaporative emmission control system incorrect purge flow

P0442 Evaporative emmission control system leak detected (small)

P0446 Evaporative emmission control system vent control circuit

Here are the code definition , They do not all mean the same, the third and fourth digit define specific fault, somponent or system