Normal Operation
WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The powertrain control module (PCM) monitors the fuel tank evaporative system for significant leaks that occur following refueling of the vehicle. If a fuel tank pressure change greater than 23.7 kPa (-7 in-Hg) of vacuum within 30 seconds after refueling occurs, or there is an excessive purge (fuel vapor) flow greater than 454 g (1.0 lb) per minute, the PCM sets DTC P0457 and sends a message to the instrument cluster over the communication network to illuminate the check fuel indicator.