Loose Gas Cap Warning Light

[sjmst]

This keep coming on, 2007 Explorer Limited V8. After a while my check engine light icon lights up. My mechanic checked the systems and all seemed fine, so he reset the light. For about a week no problems, then the loose cap light keeps popping up (no check engine light yet). Truck runs 100% perfect except for the light.
Any ideas as to what this could be?
Thanks

 

[Riken]

i could be any leak in the gas tank/filler neck. my 98 has a gas tank pressure sensor, i think your will be similar. if the ecm closes all the vent solenoids, then takes some pressure samples, then compares them. i'm assuming its pointing the finger at the gas cap whenever it detects a vapour leak. those codes won't tell you whats wrong. you have to know how to interpret them.

take a regulated air supply, set it to no more than 1-2 psi and put it in your filler neck and seal it somehow, plastic bags, anything. then have someone listen under the truck for any sounds of a leak or strong gas odors.

 

[sjmst]

Thanks!