Cadillac 2011 STS Owner's Manual page 219

The light sensor for the DRL is located on top of the
instrument panel. If the sensor is covered, it will prevent
it from sensing light, and the exterior lamps may come
on when they are not needed.
The fog lamp controls are located on the turn
signal/multifunction lever.
The band with this symbol is used to
turn the fog lamps on and off.
The parking lamps must be on for the fog lamps
to work.
To turn the fog lamps on or off, turn the fog lamp band
on the lever up to the dot and release it. The band will
return to its original position.
If the high beam headlamps are turned on, the fog
lamps will turn off. The fog lamps will come back on
when the high beam headlamps are off.
Some localities have laws that require the headlamps to
be on along with the fog lamps.
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