Ford Mercury Villager 1997 Owner's Manual page 17

Instrumentation
Service Engine Soon warning light
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 filler cap may not have been securely tightened.
These temporary malfunctions can be corrected by filling the fuel
tank with good quality fuel and/or properly tightening the
fuel filler 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.
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