GMC 2012 Terrain Owner's Manual page 130

5-14 Instruments and Controls
If the malfunction indicator lamp
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.
Notice: If the vehicle is
continually driven with this light
on, the emission controls might
not work as well, the vehicle fuel
economy might not be as good,
and the engine might not run
as smoothly. This could lead to
costly repairs that might not be
covered by the vehicle warranty.
Notice: Modifications made
to the engine, transmission,
exhaust, intake, or fuel system
of the vehicle or the replacement
of the original tires with other
than those of the same Tire
Performance Criteria (TPC)
can affect the vehicle's emission
controls and can cause this
light to come on. Modifications
to these systems could lead to
costly repairs not covered by
the vehicle warranty. This could
also result in a failure to
pass a required Emission
Inspection/Maintenance
test. See Accessories and
Modifications on page 10 3.
This light comes on during a
malfunction in one of two ways:
Light Flashing: 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.
To prevent more serious damage to
the vehicle:
Reduce vehicle speed.
Avoid hard accelerations.
Avoid steep uphill grades.
If towing a trailer, reduce the
amount of cargo being hauled
as soon as it is possible.
If the light continues to flash, stop
and park the vehicle. Turn the
vehicle off, wait at least 10 seconds,
and restart the engine. If the light is
still flashing, follow the previous
steps and see your dealer for
service as soon as possible.
Light On Steady: An emission
control system malfunction has
been detected on the vehicle.
Diagnosis and service might be
required.