Buick 1993 LeSabre Owner's Manual page 116

"Change Oil Soon'' Light (Option)
This light is activated by
the Engine Oil Life
Monitor System. It
indicates that the engine oil
has degraded enough to
require changing. See
"Engine Oil" in the Index.
After changing the engine oil, the system should be
reset.
This will cause the "Change Oil Soon" light once
again, to be lit for just the bulb check period
of 3
seconds.
This is determined by electronically monitoring engine
speed, coolant temperature and vehicle speed. Since the
change interval is dependent on driving habits and
conditions, the "Change Oil Soon" light may come on as
early as 2,000 miles or less for harsh circumstances.
The "Change Oil Soon" light is lit for three seconds as a
bulb check each time the ignition key is turned to the
RUN position. If an oil change is required, it will stay
on for 60 seconds each time the engine is started. If the
"Change Oil Soon" light is on continuously, there is a
problem with the Oil Life Monitor System and service is
required.
The reset button is inside this hole, which is under the
passenger's side of the instrument panel, near the door.
With the ignition key in the RUN position, but the
engine not started, use a pen to push the reset button,
holding it in for at least 5 seconds but not more than 60
seconds. After 5 seconds, the "Change Oil Soon" light
will flash 4 times and then turn off. This indicates that
the Oil Life Monitor System has been reset.
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