Toyota Repair: Engine Light on 04 Echo, evap purge valve, emission system

Question
Engine light keeps coming on, car seems to be running fine but codes that came back are P0441 (Evaporative Emission System Incorrect Purge Flow), P0442 (Evaporative Emission System Leak Detected (small leak)) and P0446 (Evaporative Emission System Vent Control Circuit)... my brother has the same problem with his 05 Echo... is this common? how to we resolve?

Answer
Having all of these codes indicates a large leak in the emission control evap recovery system, in most cases it's caused by either a loose or missing gas cap, another reason may be that the evap purge valve is not working at times, it's located near the air filter housing.