Normal Operation

WARNING: This page is about a different car, the 2008 Ford RV Cutaway, 2008 Ford Econoline, 2008 Ford E450 Super Duty, and 2008 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

The PCM monitors the fuel tank evaporative emission system for significant leaks that occur following refueling of the vehicle. Once the PCM detects a fuel vapor leak, the PCM sends the instrument cluster (IC) a message over the communication network to turn on the check fuel cap reconfigurable telltale indicator. DTC P0457 sets in the PCM following a successful cruise test, which is initiated when the vehicle is driven at a steady speed above 64 km/h (40 mph) for a duration of approximately 4-5 minutes. If the PCM is unable to successfully run the cruise test, the instrument cluster (IC) does not receive the check fuel cap message and the check fuel cap reconfigurable telltale indicator remains off.

If the instrument cluster (IC) does not receive the fuel cap off data from the PCM for 5 seconds or less, the instrument cluster (IC) defaults the check fuel cap indicator to the last setting, based upon the last known good data message. If the instrument cluster (IC) does not receive the fuel cap off data from the PCM for more than 5 seconds, the instrument cluster (IC) sets DTC U0100 in continuous memory and defaults the fuel cap off indicator off.

DTC P0457 (Evaporative Emission System Leak Detected [fuel cap loose/off]) - sets in the PCM 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 of greater than 454 g (1.0 lb) per minute.

This pinpoint test is intended to diagnose the following:

PCM
Instrument cluster (IC)