
Driving On Grades
Reduce speed and shift to a lower gearbeforestarting
down a long or steep downgrade. If the transmission is
not shifted down, the brakes might have to be used so
much that they would get hot and no longer work well.
Vehicles can tow in D (Drive). Shift the transmission to
a lower gear if the transmission shifts too often under
heavy loads and/or hilly conditions.
The tow/haul mode may be used if the transmission
shifts too often. SeeTow/Haul Mode Light on page 3-51.
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant will boil at a lower
temperature than at normal altitudes. If the engine is
turned off immediately after towing at high altitude on
steep uphill grades, the vehicle may show signs similar to
engine overheating. To avoid this, let the engine run while
parked, preferably on level ground, with the automatic
transmission in P (Park) for a few minutes before turning
the engine off. If the overheat warning comes on, see
Engine Overheating on page 5-36.
Parking on Hills
{CAUTION:
Parking the vehicle on a hill with the trailer
attached can be dangerous. If something goes
wrong, the rig could start to move. People can be
injured, and both the vehicle and the trailer can be
damaged. When possible, always park the rig on a
 at surface.
If parking the rig on a hill:
1. Press the brake pedal, but do not shift into P (Park)
yet. Turn the wheels into the curb if facing downhill
or into traffic if facing uphill.
2. Have someone place chocks under the trailer
wheels.
3. When the wheel chocks are in place, release the
regular brakes until the chocks absorb the load.
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A.Engine Air Cleaner/Filter on page 5-22.
B. Coolant Surge Tank and Pressure Cap.
SeeCooling System on page 5-30.
C. Positive (+) Terminal. SeeJump Starting on
page 5-46.
D.Battery on page 5-45.
E. Engine Oil Fill Cap. See “When to Add Engine Oil”
underEngine Oil on page 5-17.
F. Automatic Transmission Dipstick. See “Checking
the Fluid Level” underAutomatic Transmission Fluid
(4-Speed Transmission) on page 5-24orAutomatic
Transmission Fluid (6-Speed Transmission) on
page 5-27.
G. Remote Negative (−) Terminal (Out of View).
SeeJump Starting on page 5-46.
H. Engine Oil Dipstick (Out of View). See “Checking
Engine Oil” underEngine Oil on page 5-17.
I. Engine Cooling Fan. SeeCooling System on
page 5-30.
J. Power Steering Fluid Reservoir. SeePower Steering
Fluid on page 5-39.
K. Brake Master Cylinder Reservoir. See “Brake Fluid”
underBrakes on page 5-41.
L.Underhood Fuse Block on page 5-127.
M. Windshield Washer Fluid Reservoir. See “Adding
Washer Fluid” underWindshield Washer Fluid
on page 5-40.Engine Oil
For diesel engine vehicles, see “Engine Oil” in the
DURAMAX®Diesel manual.
Checking Engine Oil
It is a good idea to check the engine oil level at each
fuel  ll. In order to get an accurate reading, the oil must
be warm and the vehicle must be on level ground.
The engine oil dipstick handle is a yellow loop.
SeeEngine Compartment Overview on page 5-16
for the location of the engine oil dipstick.
1. Turn off the engine and give the oil several minutes
to drain back into the oil pan. If this is not done,
the oil dipstick might not show the actual level.
2. Pull out the dipstick and clean it with a paper towel
or cloth, then push it back in all the way. Remove it
again, keeping the tip down, and check the level.
5-17 

Checking Coolant
The coolant surge tank is located in the engine
compartment on the passenger side of the vehicle.
SeeEngine Compartment Overview on page 5-16
for more information on location.
The vehicle must be on a level surface when checking
the coolant level.
Check to see if coolant is visible in the coolant surge
tank. If the coolant inside the coolant surge tank is
boiling, do not do anything else until it cools down.
If coolant is visible but the coolant level is not at or
above the FULL COLD mark, add a 50/50 mixture of
clean, drinkable water and DEX-COOL
®coolant at the
coolant surge tank, but be sure the cooling system is
cool before this is done.
The coolant level should be at or above the
FULL COLD mark. If it is not, you may have a
leak in the cooling system.
If the vehicle has a low coolant sensor and the
LOW COOLANT LEVEL message comes on and
stays on, it means you are low on engine coolant.
See “LOW COOLANT LEVEL” underDIC Warnings
and Messages on page 3-66.
5-33 

4. With the coolant surge tank pressure cap off,
start the engine and let it run until the engine
coolant temperature gage indicates approximately
195°F (90°C).
By this time, the coolant level inside the coolant
surge tank may be lower. If the level is lower, add
more of the proper mixture to the coolant surge
tank until the level reaches the FULL COLD mark.
5. Replace the pressure cap. Be sure the pressure
cap is hand-tight and fully seated.
6. Verify coolant level after engine is shut off and the
coolant is cold. If necessary, repeat coolant  ll
procedure Steps 1 through 6.
Notice:If the pressure cap is not tightly installed,
coolant loss and possible engine damage may occur.
Be sure the cap is properly and tightly secured.
Engine Overheating
If the vehicle has the DURAMAX®Diesel engine, see
the DURAMAX®Diesel manual for more information.
The vehicle has several indicators to warn of engine
overheating.
You will  nd a coolant temperature gage on the vehicle’s
instrument panel. SeeEngine Coolant Temperature
Gage (US-Canada) on page 3-44.In addition, you will  nd ENGINE OVERHEATED STOP
ENGINE, ENGINE OVERHEATED IDLE ENGINE,
and ENGINE POWER IS REDUCED messages in the
Driver Information Center (DIC) on the instrument panel.
SeeDIC Warnings and Messages on page 3-66.
You may decide not to lift the hood when this warning
appears, but instead get service help right away.
SeeRoadside Assistance Program on page 7-7.
If you do decide to lift the hood, make sure the vehicle
is parked on a level surface.
Then check to see if the engine cooling fans are
running. If the engine is overheating, both fans should
be running. If they are not, do not continue to run
the engine and have the vehicle serviced.
Notice:Engine damage from running your engine
without coolant is not covered by your warranty.
SeeOverheated Engine Protection Operating Mode
on page 5-38for information on driving to a safe
place in an emergency.
Notice:If the engine catches  re while driving
with no coolant, the vehicle can be badly damaged.
The costly repairs would not be covered by the
vehicle warranty. SeeOverheated Engine Protection
Operating Mode on page 5-38for information on
driving to a safe place in an emergency.
5-36