Ford Mustang Owner's Manual page 128

The Air Bag Supplemental Restraint System
consists of:
driver and passenger air bag modules (which
include the inflators and air bags),
one or more impact and safing sensors,
a system diagnostic module,
a readiness light and tone,
and the electrical wiring which connects the
components.
The diagnostic module monitors its own circuits,
the air bag electrical system, the air bag
readiness light, the air bag power, and the air
bag inflators.
Determining if System Is Operational
The Air Bag Supplemental Restraint System uses
a readiness light and a tone to indicate the
condition of the system. The readiness light is in
the instrument cluster. When you turn the
ignition key to ON, this light will illuminate for
approximately six (6) seconds and then turn off.
This indicates that the system is operating
normally. NOTE: Routine maintenance of the air
bag system is not required.
A problem with the system is indicated by one
or more of the following:
the readiness light will either flash or stay lit,
the readiness light will not light immediately
after ignition is turned on,
a group of five beeps will be heard. The tone
pattern will repeat periodically until the
problem and light are repaired.
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