FORD 2005 Expedition v.2 - Manual (Page 240)

parked. The Low Tire Warning Lamp will turn ON if the tire pressure is
25% below the pressure listed on the tire label (approximately 6 to 9 psi
below the manufacturer’s recommend tire pressure). If the tire pressure
increases 2 psi above the “Light ON” threshold, then the TPMS light will
turn OFF. Once the light is illuminated, your tires are under inflated and
need to be inflated to the manufacturer’s recommended tire pressure.
Even if the light turns ON and a short time later turns OFF, your tire
pressure still needs to be checked.
In short, once the light has turned ON, at least one tire may be under
inflated.
When your temporary spare tire is installed
When one of your road tires needs to be replaced with the temporary
spare, the TPMS system will continue to identify an issue to remind you
that the damaged road wheel/tire needs to be repaired and put back on
your vehicle. During this time, the low tire warning light can periodically
return or stay on, depending on the state of the damaged road
wheel/tire. This will include the message center messages (if equipped).
To restore the full functionality of the Tire Pressure Monitoring System,
have the damaged road wheel/tire repaired and remounted on your
vehicle. For additional information, refer to Changing tires with TPMS
in this section.
When you believe your system is not operating properly
The main function of the Tire Pressure Monitoring System is to warn you
when your tires need air. It can also warn you in the event the system is
no longer capable of functioning as intended. Please refer to the
following chart for information concerning your Tire Pressure Monitoring
System:
2005 Expedition (exd)
Owners Guide (post-2002-fmt)
USA_English (fus)
Tires, Wheels and Loading
240