I have a 2004 F150 XLT 4x2 5.4 liter Supercab- First the check fuel cap message came on -then later check engine light came on -Truck runs fine -Fuel cap seems to fit tight but message keeps coming back.I disconnected the battery and fuel cap warning disappeared but came back after two weeks along with check engine light. One mechanic said that fuel tank vent may be the problem- Without involving dealer , any suggestions as to how to correct?

 

Go to autozone or advance auto, and have them scan the computer with a code reader. They will do it for free. Bring the CODE they give you back here, and we'll tell ya what's wrong with your truck, and how to fix it. There's a lot of knowledgable guys here...

 

If you're in your 3/36 warranty, the dealer is the best and easiest choice. Since your CHECK GAS CAP light is on, you likely have an evaporative emissions system leak. In most circumstances, this is covered under the federally mandated emissions warranty that is usually 8/80.

First, have the code read so you actually know what the SES is trying to tell you. This will require a CAN-capable OBD-II scan tool. You can buy your own at Wal-Mart for $65. Many autoparts stores read codes for free. Before having it read, make certain that their scanner is up to date. Most are not and will not communicate with your truck's computer.

Until you have the DTC, we can only make an educated guess.

Steve