Engine Code P4056 - Evaporative Emission Control System Very Small Leak Detected
 

Yesterday morning after I start the car after 12 hours of parking at work, I notice my Service Engine Soon light has come on. Get back home, run the diagnostic scanner and see this code thrown.

A quick Google search shows me these possible causes:
- Missing or loose fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- Evaporative Emission (EVAP) canister or fuel tank leaks
- Evaporative Emission (EVAP) system hose leaking
- Fuel tank leaking

There is no noticeable fuel smell, none stronger than usual I suppose I should say. I do have an aftermarket exhaust and headers so it is possible I've just become accustomed to a certain...eau de Z odor in and around my car...but I'd like to think I'd smell it if something was leaking pertaining to my fuel line.

I'm not sure what could have happened over the course of 12 hours stationary at work to set this off, but I'd like some input as to simple things I might be able to check from home without a full garage. That means pretty much whatever I need to install my boltons and a few other odds and ends. I'm no full service mechanic.

Should it be easier to run it to Nissan...how long do ya'll think they'd take to run a scan and find the source? You know...with the hourly charge and all. They know me up there so I don't think they'd try to jerk me around too much, but I'd like to have a ballpark anyway.

I appreciate the time, guys and gals.

Often caused by a loose or damaged gas cap.

Unfortunately, one of the first things I tried with no luck.

Start looking for leaks. FSM will have locations of hoses, canisters, &c.