Buick 2010 Lacrosse Owner's Manual page 106

If a short distance must be driven
with the light on, be sure to turn off
all accessories, such as the radio
and air conditioner.
A computer system called OBD II
(On-Board Diagnostics-Second
Generation) monitors operation of
the fuel, ignition, and emission
control systems. It ensures that
emissions are at acceptable levels
for the life of the vehicle, helping to
produce a cleaner environment.
This light comes on when the
ignition is on, but the engine is not
running, as a check to show it is
working. If it does not, have
the vehicle serviced by your
dealer/retailer.
If the check engine light comes on
and stays on, while the engine is
running, this indicates that there is
an OBD II problem and service is
required.
Malfunctions often are indicated by
the system before any problem is
apparent. Being aware of the light
can prevent more serious damage
to the vehicle. This system assists
the service technician in correctly
diagnosing any malfunction.
This light comes on during a
malfunction in one of two ways:
A misfire condition
has been detected. A misfire
increases vehicle emissions and
could damage the emission control
system on the vehicle. Diagnosis
and service might be required.