Pontiac 2005 Aztek Owner's Manual page 152

Retro-Active Reset
The trip odometer has a feature called retro-active
reset. This feature can be used to set the trip odometer
to the number of miles or kilometers driven since the
ignition was last turned on. This can be used if you
forget to reset your trip odometer at the beginning of a
trip. To use the retro-active reset feature, push and
hold the trip/reset button for at least three seconds.
The trip odometer will then display the number of miles
or kilometers driven since the ignition was last turned
on and you began driving. If you use the retro-active
reset feature after you have started the vehicle,
but before you begin moving, the display will show the
number of miles or kilometers you drove during the
last ignition cycle. Once you begin driving, the trip
odometer will accumulate mileage. For example,
if you have driven 5.0 miles (8.0 km) since you started
your vehicle, and then activate the retro-active reset
feature, the display will show 5.0 miles (8.0 km).
As you drive, the display will then increase to
5.1 miles (8.2 km), 5.2 miles (8.4 km), etc.
3-30
Tachometer
The tachometer located
on your instrument panel
displays the engine
speed in revolutions per
minute (rpm).