GMC 2.8L Duramax Diesel 2020 Manual page 30

Fill the DEF tank on level ground
and with the vehicle off. When
adding DEF, it is recommended to
fully fill the DEF tank. For DEF tank
capacity see Capacities and
Specifications 0 97. When adding
DEF to an empty or very low tank,
always add at least 7.5L (2 gal) of
fluid to release the vehicle from
speed limitation.
When fluid reaches the top of the
DEF fill pipe, stop filling. Do not top
off the DEF tank. If using a bottle or
jug to refill DEF, follow the
instructions on the container label
and use a dedicated fill aid.
Caution
Do not overfill the DEF tank and
do not allow DEF to contact the
finished surfaces of the vehicle,
as it could damage the vehicle
finish. If DEF is spilled during
filling, wipe any affected surface
with a damp cloth.
Make sure the cap is fully installed.
Push the fuel/DEF door closed.
DEF Low
As the DEF level drops, warnings
will automatically be displayed in the
Driver Information Center (DIC).
Select Vehicle Information in the
DIC to view DEF level status. See
Driver Information Center (DIC)
0 13.
Refill the DEF tank at the first
opportunity after a low warning
indication to avoid vehicle speed
limitations.
It may take some time for the
vehicle to detect that DEF has been
added. If there was a vehicle speed
limitation, it will be removed
gradually and it may take several
kilometers/miles for the DIC
message to update.
If DEF is added under freezing
conditions, especially if DEF level is
low and frozen, up to several hours
of drive time may be required to
remove the speed limitation. It is
recommended to ensure the DEF
tank level is 30% or higher during
winter time.
Driving and Operating
The DEF range DIC message first
displays at approximately 1 600 km
(1,000 mi). This message appears
again at approximately 500 km
(300 mi) of remaining range before
the exhaust fluid tank becomes
empty.
As the fluid level nears empty, these
messages appear every time the
vehicle is started.
If the DEF low warnings are ignored
and the DEF tank becomes empty,
the DIC will display messages that
describe the action needed and
distance until vehicle speed is
limited. For the DEF warning light
symbol, see Diesel Exhaust Fluid
(DEF) Warning Light 0 13.
DEF Quality Poor
Use only DEF that is GM approved,
or fluid containing the API certified
or ISO 22241 label.
DEF has an expiration date. If the
system detects poor quality,
or contaminated or diluted DEF, the
DIC message will display along with
distance until vehicle speed is
limited.
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