Ford 1999 Taurus Owner's Manual page 52

If the light does not come ON when the TCS is
depressed or if the light FLASHES when you are
driving, have your vehicle serviced at the first
opportunity. If this condition persists, damage could
occur to the transmission.
Anti-Theft Alarm Light
This light is used when you set the anti-theft alarm
system. See the Controls and Features chapter later
in this guide for more information.
This light will also flash if the passive anti-theft
system is not functioning correctly. If the light
continues to flash have the system serviced at your
Ford or Lincoln-Mercury dealer immediately.
NOTE: If this light flashes rapidly, the vehicle will
be disabled.
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