Ford 1996 Thunderbird Manual page 67

If the light turns on and off on rare occasions
while you are driving, it means that a
malfunction occurred and the condition corrected
itself.
An example of a condition which corrects itself
occurs when an engine running out of fuel
begins to misfire. In this case, the Check Engine
Warning Light may turn on and will then set a
Diagnostic Trouble Code indicating that the
engine was misfiring while the last of the fuel
was being consumed. After refueling, the Check
Engine Warning Light will turn off after the
vehicle has completed three consecutive warm
up cycles without a misfire condition occurring.
A warm up cycle consists of engine start from a
cold condition (engine at ambient temperature)
and running until the engine reaches normal
operating temperature.
On the fourth engine start up, the Check Engine
Warning Light will turn off as soon as the
engine begins to crank. It is not necessary to
have the engine serviced.
Under certain conditions, the Check Engine
Warning Light may come on if the fuel cap is
not properly installed. If the Check Engine
Warning Light comes on and you suspect that
the fuel cap is not properly installed, pull off the
road as soon as it is safely possible and turn off
the engine. Remove and replace the fuel cap,
making sure it is properly seated.
After completing the three consecutive warm up
cycles and on the fourth engine start up, the
Check Engine Warning Light should turn off. If
the light does not go off after the fourth engine
restart, have your vehicle serviced by your
dealer or a qualified technician.
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