Check Fuel Cap
WARNING: This page is about a different car, the 2004 Mercury Monterey and 2004 Ford Freestar. However, it is still accessible from the selected car via links, so may be relevant.
The check fuel cap indicator is used to indicate significant leaks in the fuel tank evaporative system due to a loose fuel cap. Fuel tank pressure is monitored by the PCM and if a leak is detected it signals a fault to the instrument cluster over the SCP network. Once the PCM has detected a loose fuel cap and the indicator is illuminated, the indicator will remain illuminated until the fuel cap is secured and the ignition switch has been cycled one time.