FORD 2008 Explorer v.3 - Manual (Page 245)

Understanding your Tire Pressure Monitoring System (TPMS)
The Tire Pressure Monitoring System measures pressure in your four
road tires and sends the tire pressure readings to your vehicle. The Low
Tire Pressure Warning Lamp will turn ON if the tire pressure is
significantly low. 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. Visit www.checkmytires.org
for additional information.
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.
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:
Tires, Wheels and Loading
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