2009 Crew, 4.7, 39k. Several days ago the gas cap indicator came on followed by the MIL light. The cap was secure, previous fill up was several days earlier. The code reader gave a P0457. I replaced the cap and cleared the indicator and the obd2 code but they both returned after the next start up. So apparently there is something else with the EVAP system. I really hate going to the stealer, so does anyone have a suggestion before I stoop that low?

 

The EVAP canister in the 2009 4.7 is underneath the truck somewhere next to the frame. The service manual shows that there are 4 types of canister used so I can't help you there. Look underneath to see if something is damaged or loose. Crawl underneath and follow the hoses from the gas tank.

There is also a purge solenoid under the hood, should be easy to find next to the firewall, check that out as well.

Also, the manual shows the EVAP system to be part of the Emissions Control which may be covered under the longer warranty. I would argue that it's under warranty due to the Feds mandating it. It may also be mandated in your state.

 

Do a good inspection on the gas cap, if you have not already, and make sure there are no cracks in it.