GMC Cadillac CT5 2021 Manual page 105

104 INSTRUMENTS AND CONTROLS
been detected and the vehicle may
require service. The light should come
on to show that it is working when
the ignition is in Service Mode. See
Ignition Positions 0 223.
Malfunctions are often indicated by
the system before any problem is
noticeable. Being aware of the light
and seeking service promptly when it
comes on may prevent damage.
Caution
If the vehicle is driven continually
with this light on, the emission
control system may not work as
well, the fuel economy may be
lower, and the vehicle may not run
smoothly. This could lead to costly
repairs that might not be covered
by the vehicle warranty.
Caution
Modifications to the engine,
transmission, exhaust, intake,
or fuel system, or the use of
replacement tires that do not meet
the original tire specifications, can
cause this light to come on. This
could lead to costly repairs not
covered by the vehicle warranty.
This could also affect the vehicle s
ability to pass an Emissions
Inspection/Maintenance test. See
Accessories and Modifications 0 309.
If the light is flashing : A
malfunction has been detected that
could damage the emission control
system and increase vehicle
emissions. Diagnosis and service may
be required.
To help prevent damage, reduce
vehicle speed and avoid hard
accelerations and uphill grades.
If towing a trailer, reduce the amount
of cargo being hauled as soon as
possible.
If the light continues to flash, find a
safe place to park. Turn the vehicle off
and wait at least 10 seconds before
restarting the engine. If the light is
still flashing, follow the previous
guidelines and see your dealer for
service as soon as possible.
If the light is on steady : A
malfunction has been detected.
Diagnosis and service may be
required.
Check the following:
If fuel has been added to the vehicle
using the capless fuel funnel
adapter, make sure that it has been
removed. See Filling the Tank with
a Portable Gas Can under Filling the
Tank 0 297. The diagnostic system
can detect if the adapter has been
left installed in the vehicle, allowing
fuel to evaporate into the
atmosphere. A few driving trips with
the adapter removed may turn off
the light.
Poor fuel quality can cause
inefficient engine operation and
poor driveability, which may go
away once the engine is warmed up.
If this occurs, change the fuel