GMC Duramax Diesel 2015 Owner's Manual page 18

This light may also come on when
the Diesel Exhaust Fluid (DEF)
management system is not working.
See Diesel Exhaust Fluid on
page 9-13.
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 also
assists the service technician in
correctly diagnosing any
malfunction.
Caution
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.
Caution
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 10-1.
When the light is on, an emission
control system malfunction has
been detected on the vehicle.
Diagnosis and service might be
required.
Instruments and Controls
An emission system malfunction
might be corrected by using good
quality fuel. Poor fuel quality causes
the engine not to run as efficiently
as designed and may cause: stalling
after start-up, stalling when the
vehicle is changed into gear,
misfiring, hesitation on acceleration,
or stumbling on acceleration. These
conditions might go away once the
engine is warmed up. See Fuel for
Diesel Engines on page 9-21.
If this does not make the light turn
off, your dealer can check the
vehicle. The dealer has the proper
test equipment and diagnostic tools
to fix any mechanical or electrical
problems that might have
developed.
Emissions Inspection and
Maintenance Programs
Depending on where you live, your
vehicle may be required to
participate in an emission control
system inspection and maintenance
program. For the inspection, the
5-9