GMC Sierra Denali 2017 Owner's Manual page 306

The trailer must be equipped
with brakes adequate for the
intended use. A loaded trailer
weighing more than 900 kg
(2,000 lb) must be equipped with
its own brake system, with
brakes working on all axles.
Trailer braking equipment
conforming to Canadian
Standards Association (CSA)
requirement CAN3-D313, or its
equivalent, is recommended.
Do not tow a trailer during the
first 800 km (500 mi) to prevent
damage to the engine, axle,
or other parts.
Then during the first 800 km
(500 mi) of trailer towing, do not
drive over 80 km/h (50 mph) and
do not make starts at full throttle.
Vehicles can tow in D (Drive).
The Tow/Haul Mode may be
used if the transmission shifts
too often. See Tow/Haul
Mode 0 273.
Turn off Park Assist when
towing.
Warning
When towing a trailer, exhaust
gases may collect at the rear of
the vehicle and enter if the
liftgate, trunk/hatch, or rear-most
window is open.
When towing a trailer:
Do not drive with the
liftgate, trunk/hatch,
or rear-most window open.
Fully open the air outlets on
or under the instrument
panel.
Also adjust the climate
control system to a setting
that brings in only outside
air. See Climate Control
Systems in the Index.
For more information about
carbon monoxide, see Engine
Exhaust 0 266.
Towing a trailer requires a certain
amount of experience. The
combination you are driving is
longer and not as responsive as the
Driving and Operating
vehicle itself. Get acquainted with
the handling and braking of the rig
before setting out for the open road.
The structure, tires, and brakes of
the trailer must be rated to carry the
load. Inadequate trailer equipment
can cause the combination to
operate in an unexpected or unsafe
manner.
Before starting, check all trailer hitch
parts and attachments, safety
chains, electrical connectors, lamps,
tires, and mirrors. Get familiar with
the handling and braking of the rig.
If the trailer has electric brakes, start
the combination moving and then
apply the trailer brake controller by
hand to be sure the brakes work.
During the trip, check occasionally
to be sure that the load is secure
and the lamps and any trailer
brakes still work.
Following Distance
Stay at least twice as far behind the
vehicle ahead as you would when
driving the vehicle without a trailer.
This can help to avoid heavy
braking and sudden turns.
305