GMC 2009 Sierra 1500 Crew Cab Owner's Manual page 240

Fuel Range
Press the trip/fuel button until FUEL RANGE displays.
This display shows the approximate number of remaining
miles (mi) or kilometers (km) the vehicle can be driven
without refueling. The display will show LOW if the fuel
level is low.
The fuel range estimate is based on an average of the
vehicle's fuel economy over recent driving history and the
amount of fuel remaining in the fuel tank. This estimate
will change if driving conditions change. For example, if
driving in traffic and making frequent stops, this display
may read one number, but if the vehicle is driven on a
freeway, the number may change even though the same
amount of fuel is in the fuel tank. This is because different
driving conditions produce different fuel economies.
Generally, freeway driving produces better fuel economy
than city driving. Fuel range cannot be reset.
Average Economy
Press the trip/fuel button until AVG ECONOMY displays.
This display shows the approximate average miles per
gallon (mpg) or liters per 100 kilometers (L/100 km).
This number is calculated based on the number of mpg
(L/100 km) recorded since the last time this menu item
was reset. To reset AVG ECONOMY, press and hold the
set/reset button.
3-56
Fuel Used
Press the trip/fuel button until FUEL USED displays. This
display shows the number of gallons (gal) or liters (L) of
fuel used since the last reset of this menu item. To reset
the fuel used information, press and hold the set/reset
button while FUEL USED is displayed.
Timer
Press the trip/fuel button until TIMER displays. This
display can be used as a timer.
To start the timer, press the set/reset button while TIMER
is displayed. The display will show the amount of time
that has passed since the timer was last reset, not
including time the ignition is off. Time will continue to be
counted as long as the ignition is on, even if another
display is being shown on the DIC. The timer will record
up to 99 hours, 59 minutes and 59 seconds (99:59:59)
after which the display will return to zero.
To stop the timer, press the set/reset button briefly while
TIMER is displayed.
To reset the timer to zero, press and hold the set/reset
button while TIMER is displayed.