Ford Repair: 2004 Ford Explorer, emissions control, ventilation system

Question
I have a 2004 Ford Explorer and my check engine light is on as well as the check gas cap light.  I took it to Advance Auto for them to run a check on the codes and it came back with an Evap emissions control system leak large error.  The check fuel cap light did not come on at the same time as the check engine light, it came on a week later.  When the car is in idle there is a noise coming from under the car.  Any ideas?

Answer
Hello Harry, If the gas cap did not get tight after a fill that will cause both lites to come on, 1st the lites need to be turned off by a diagnostic tool or disconnecting the battery for 5 minutes. Drive to see if the light comes back on. If it does then it needs to be checked for a vapor leak from the gas tank ventilation system. Hope this helps Thanks Tony