FORD 2000 Expedition - Manual (Page 9)

What you should do if the Service Engine Soon light illuminates
Light turns on solid:
This means that the OBD II system has detected a malfunction.
Temporary malfunctions may cause your Service Engine Soon light to
illuminate. Examples are:
1. The vehicle has run out of fuel. (The engine may misfire or run
poorly.)
2. Poor fuel quality or water in the fuel.
3. The fuel cap may not have been properly installed and securely
tightened.
These temporary malfunctions can be corrected by filling the fuel tank
with high quality fuel of the recommended octane and/or properly
installing and securely tightening the gas cap. After three driving cycles
without these or any other temporary malfunctions present, the Service
Engine Soon light should turn off. (A driving cycle consists of a cold
engine startup followed by mixed city/highway driving.) No additional
vehicle service is required.
If the Service Engine Soon light remains on, have your vehicle serviced
at the first available opportunity.
Light is blinking:
Engine misfire is occurring which could damage your catalytic converter.
You should drive in a moderate fashion (avoid heavy acceleration and
deceleration) and have your vehicle serviced at the first available
opportunity.
Under engine misfire conditions, excessive exhaust temperatures
could damage the catalytic converter, the fuel system, interior
floor coverings or other vehicle components, possibly causing a fire.
Air bag readiness
Momentarily illuminates when the
ignition is turned ON. If the light
fails to illuminate, continues to flash
or remains on, have the system
serviced immediately.
Instrumentation
9