Chevrolet 2010 Impala Owner's Manual page 169

The speedometer shows the vehicle's speed in both
miles per hour (mph) and kilometers per hour (km/h).
The odometer shows how far the vehicle has been
driven in either miles (used in the United States) or
in kilometers (used in Canada).
This vehicle has a tamper-resistant odometer. If the
odometer displays ERROR, it probably has been
tampered with and the numbers might not be accurate.
If the vehicle needs a new odometer installed, it must
be set to the mileage total of the old odometer. If that is
not possible, then it will be set at zero and a label must
be put on the driver's door to show the old mileage
reading of the vehicle when the new odometer was
installed.
The tachometer displays the engine speed in
revolutions per minute (rpm).
When the engine is started, a chime sounds for
several seconds to remind a driver to fasten the safety
belt, unless the driver safety belt is already buckled.
This chime and light are repeated if the driver remains
unbuckled and the vehicle is in motion. If the driver
safety belt is already buckled, neither the chime nor
the light comes on.
The safety belt light
comes on and stays on
for several seconds, then
flashes for several more.
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