Ford 1996 Bronco Manual page 81

Check engine warning light symbol
Modification or additions to the vehicle may
cause incorrect operation of the OBD II system.
Additions such as burglar alarms, cellular
phones, and CB radios must be carefully
installed. Do not install these devices by tapping
into or running wires close to powertrain control
system wires or components.
The light comes on briefly when you turn the
ignition key to ON, but it should turn off when
the engine starts. If the light does not come on
when you turn the ignition to ON or if it comes
on and stays on when you are driving, have
your vehicle serviced as soon as possible. This
indicates a possible problem with one of the
vehicle's emission control systems. You do not
need to have your vehicle towed in.
If the light turns on and off at one (1) second
intervals while you are driving the vehicle, it
means that the engine is misfiring. If this
condition persists, damage could occur to the
engine or catalytic convertor. Have your vehicle
serviced at the first opportunity. You do not
need to have your vehicle towed in.
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.
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