I have an '07 Dodge Ram SXT, 3.9 V6. Have had the CEL and 'gas cap' notice on the dash. Replaced gas cap (with OEM), reset the CEL and its been 'off' for five days now. But, I'm still getting the 'gas cap' notice. Again, new cap.

The gas cap seems to be a familiar warning, but replacing the cap usually seems to solve the problem.

 

MIne has the same gas cap notice in the dash.. but i know mine is from the rubber hose under the truck by the tranny, is broken. repaired it once and the "gas cap" went away till my temp fix got ripped.. offroading.
So you might check the hoses going to the box in front of the Gas tank. not sure what the name of it is

 

Agreed, Although you replace d or fixed the cap, you may have a vacuum leak elsewhere. Just gotta get under the truck and look around

 

evap canister, my "gas cap" light came on (small evap leak detected) my issue was the canister had a crack in it.

 

Thanks guys! I've looked around previously, but will give all those rubber hoses a closer look.