Cadillac 2011 STS Owner's Manual page 252

This light indicates that oil is not going through the
engine quickly enough to keep it lubricated. The engine
could be low on oil or could have some other oil
problem. Have the vehicle serviced by your dealer.
The oil light could also come on in the following
situations:
The light comes on briefly when the ignition is
turned on to show that it is working properly. If it
does not come on with the ignition on, there may
be a problem with the fuse or bulb. Have the
vehicle serviced by your dealer.
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For vehicles with an oil
pressure light, if there is a
problem with the oil, the
light may stay on after
the engine is started,
or comes on while driving.
Sometimes when the engine is idling at a stop, a
chime sounds and the light may blink on and off.
This is normal.
Do not keep driving if the oil pressure is low. The
engine can become so hot that it catches fire.
Someone could be burned. Check the oil as soon
as possible and have the vehicle serviced.