Automatic Transmission Operation
(Six Speed Automatic Transmission)............3-27
Automatic Transmission Operation
(Four Speed Automatic Transmission)..........3-32
Tow/Haul Mode ............................................3-34
Parking Brake..............................................3-36
Shifting Into Park..........................................3-37
Shifting Out of Park......................................3-38
Parking Over Things That Burn.......................3-39
Engine Exhaust............................................3-40
Running the Vehicle While Parked..................3-41Mirrors...........................................................3-42
Manual Rearview Mirror.................................3-42
Outside Manual Mirrors..................................3-42
Outside Towing Mirrors..................................3-42
Outside Power Mirrors...................................3-43
Outside Convex Mirror...................................3-43
Outside Heated Mirrors..................................3-44
Storage Areas................................................3-44
Section 3 Features and Controls
3-2
B (ACC/ACCESSORY):This is the position in which
you can operate things like the radio and the windshield
wipers when the engine is off.
C (ON/RUN):This position can be used to operate the
electrical accessories and to display some instrument
panel cluster warning and indicator lights. The
switch stays in this position when the engine is running.
If you leave the key in the ACC/ACCESSORY or
ON/RUN position with the engine off, the battery could
be drained. You may not be able to start the vehicle
if the battery is allowed to drain for an extended period
of time.
D (START):This is the position that starts the engine.
When the engine starts, release the key. The ignition
switch returns to ON/RUN for driving.
A warning tone will sound when the driver door is
opened, the ignition is in ACC/ACCESSORY or
LOCK/OFF and the key is in the ignition.Retained Accessory Power (RAP)
These vehicle accessories can be used for up to
10 minutes after the engine is turned off:
•Audio System
•Power Windows (if equipped)
These features will work when the ignition key is in
ON/RUN or ACC/ACCESSORY. Once the key is turned
from ON/RUN to LOCK/OFF, power to the radio will
continue to work 10 minutes or until the driver door is
opened. The power windows will continue to work for up
to 10 minutes or until any door is opened.
Starting the Engine
If the vehicle has the DURAMAX®Diesel engine, see
the DURAMAX®Diesel manual for more information.
To place the transmission in the proper gear:
Move the shift lever to P (Park) or N (Neutral). The
engine will not start in any other position. To restart the
engine when the vehicle is already moving, use
N (Neutral) only.
3-23
Fast Idle System
Fast Idle System with Switch
If the vehicle has this feature it is available only with
cruise control. The manual fast idle switch is operated
using the cruise control buttons located on the left
hand side of the steering wheel.
This system can be used to increase engine idle speed
whenever the following conditions are met:
•The park brake is set.
•The brake pedal is not pressed.
•The vehicle must not be moving and the accelerator
must not be pressed.
To control the fast idle:
•To Enable the Fast idle, press and release the
Cruise Control On/Off button and ensure that
the LED is lit.
•For the preset Fast Idle, press and release the
cruise set switch. This will set the preset fast
idle speed.
•For the variable fast idle, press and hold the
accelerator at the desired RPM, then press
and release the cruise control cruise set switch to
set the desired idle speed.When the fast idle is active the Driver Information
Center (DIC) will display “FAST IDLE ON.”
One of the following actions will turn off the fast idle:
•Pressing the brake.
•Selecting the Cancel button.
•Releasing the Parking Brake.
•The transmission shifter is moved out of P (Park) or
N (Neutral).
•Selecting the cruise control on/off button when it
was previously on.
Engine Coolant Heater
If the vehicle has the DURAMAX Diesel engine, see the
DURAMAX Diesel manual for more information.
The engine coolant heater can provide easier starting
and better fuel economy during engine warm-up in cold
weather conditions at or below 0°F (−18°C). Vehicles
with an engine coolant heater should be plugged
in at least four hours before starting. An internal
thermostat in the plug-end of the cord may exist which
will prevent engine coolant heater operation at
temperatures above 0°F (−18°C).
3-25
The vehicle has a shift stabilization feature that adjusts
the transmission shifting to the current driving
conditions in order to reduce rapid upshifts and
downshifts. This shift stabilization feature is designed to
determine, before making an upshift, if the engine is
able to maintain vehicle speed by analyzing things such
as vehicle speed, throttle position, and vehicle load.
If the shift stabilization feature determines that a current
vehicle speed cannot be maintained, the transmission
does not upshift and instead holds the current gear.
In some cases, this could appear to be a delayed shift,
however the transmission is operating normally.
The transmission uses adaptive shift controls. Adaptive
shift controls continually compares key shift parameters
to pre-programmed ideal shifts stored in the
transmissions computer. The transmission constantly
makes adjustments to improve vehicle performance
according to how the vehicle is being used, such as with
a heavy load or when temperature changes. During this
adaptive shift control process, shifting might feel different
as the transmission determines the best settings.
The shift quality of a new vehicle may not be ideal
because the Adaptive Shift Control process may not
have determined the best settings for a particular shift or
condition. Shift quality will improve with continued
driving.When temperatures are very cold, the transmission’s
gear shifting could be delayed providing more stable
shifts until the engine warms up. Shifts could be more
noticeable with a cold transmission. This difference
in shifting is normal.
M (Manual Mode):This position lets drivers select
the range of gears appropriate for current driving
conditions. If the vehicle has this feature, see Range
Select Mode later in this section.
3 (Third):This position is also used for normal driving.
It reduces vehicle speed more than D (Drive) without
using the brakes. You might choose 3 (Third) instead of
D (Drive) when driving on hilly, winding roads, when
towing a trailer, so there is less shifting between gears
and when going down a steep hill. See Range Select
Mode later in this section.
2 (Second):This position reduces vehicle speed even
more than 3 (Third) without using the brakes. You
can use 2 (Second) on hills. It can help control vehicle
speed as you go down steep mountain roads, but
then you would also want to use the brakes off and on.
See Range Select Mode later in this section.
If you manually select 2 (Second) in an automatic
transmission, the transmission will start in second gear.
You can use this feature for reducing the speed of
the rear wheels when you are trying to start the vehicle
from a stop on slippery road surfaces.
3-29
To use this feature, do the following:
1. Move the shift lever to M (Manual Mode).
2. Press the plus/minus buttons, located on the
steering column shift lever, to select the desired
range of gears for current driving conditions.
When M (Manual Mode) is selected a number displays
in the DIC next to the M indicating the current gear.
This number is the highest gear that can be used.
However, the vehicle can automatically shift to lower
gears as it adjusts to driving conditions. This means that
all gears below that number are available. When
5 (Fifth) is selected, 1 (First) through 5 (Fifth) gears are
automatically shifted by the vehicle, but 6 (Sixth)
cannot be used until the plus/minus button located on
the steering column lever is used to change to the gear.
Grade Braking is not available when Range Selection
Mode is active. SeeTow/Haul Mode on page 3-34.While using Range Selection Mode, cruise control and
the Tow/Haul mode can be used.
Notice:Spinning the tires or holding the vehicle in
one place on a hill using only the accelerator
pedal may damage the transmission. The repair will
not be covered by the vehicle warranty. If you
are stuck, do not spin the tires. When stopping on a
hill, use the brakes to hold the vehicle in place.
Low Traction Mode
Low Traction Mode can assist in vehicle acceleration
when road conditions are slippery. While the vehicle is at
a stop, select the second gear range using Range
Selection Mode. This will limit torque to the wheels after
it detects wheel slip, preventing the tires from spinning.
3-31
Parking on Hills
{WARNING:
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
flat surface.
If parking the rig on a hill:
1. Press the brake pedal, but do not shift the
transmission 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
brake pedal until the chocks absorb the load.
4. Reapply the brake pedal. Then apply the parking
brake and shift into P (Park).
5. Release the brake pedal.
Leaving After Parking on a Hill
1. Apply and hold the brake pedal while you:
•start the engine,
•shift into a gear, and
•release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the
chocks.
Maintenance When Trailer Towing
The vehicle needs service more often when pulling a
trailer. See this manual’s Maintenance Schedule
or Index for more information. Things that are especially
important in trailer operation are automatic transmission
fluid, engine oil, axle lubricant, belts, cooling system
and brake system. It is a good idea to inspect
these before and during the trip.
Check periodically to see that all hitch nuts and bolts
are tight.
5-41
A. Battery. SeeBattery on page 6-43.
B. Radiator Pressure Cap. SeeCooling System on
page 6-28.
C. Coolant Recovery Tank. SeeCooling System on
page 6-28.
D. Automatic Transmission Fluid Dipstick. See
“Checking the Fluid Level” underAutomatic
Transmission Fluid (4-Speed Transmission)
on page 6-21orAutomatic Transmission Fluid
(6-Speed Transmission) on page 6-24.
E. Engine Oil Fill Cap. See “When to Add Engine Oil”
underEngine Oil on page 6-15.
F. Engine Oil Dipstick. See “Checking Engine Oil”
underEngine Oil on page 6-15.
G. Engine Air Cleaner/Filter. SeeEngine Air
Cleaner/Filter on page 6-20.
H. Power Steering Fluid Reservoir. SeePower Steering
Fluid on page 6-38.
I. Brake Master Cylinder Reservoir. See “Brake Fluid”
underBrakes on page 6-40.
J. Windshield Washer Fluid Reservoir. See “Adding
Washer Fluid” underWindshield Washer Fluid
on page 6-39.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 fill. 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 6-14
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.
6-15
To inspect or replace the engine air cleaner/filter, do the
following:
1. Unhook the retainer clips and remove the cover.
2. Lift the filter out of the engine air cleaner/filter
housing. Care should be taken to dislodge as
little dirt as possible.
3. Clean the engine air cleaner/filter housing.
4. Inspect or replace the engine air cleaner/filter.
Make sure that the filter fits properly into the
housing.
5. Reinstall the cover and fasten the retaining clips.
{WARNING:
Operating the engine with the air cleaner/filter off
can cause you or others to be burned. The air
cleaner not only cleans the air; it helps to stop
flames if the engine backfires. If it is not there and
the engine backfires, you could be burned. Do not
drive with it off, and be careful working on the
engine with the air cleaner/filter off.Notice:If the air cleaner/ lter is off, a back re
can cause a damaging engine re. And, dirt
can easily get into the engine, which will damage it.
Always have the air cleaner/ lter in place when
you are driving.
Automatic Transmission Fluid
(4-Speed Transmission)
If your vehicle has the DURAMAX Diesel engine, see
the DURAMAX Diesel manual for more information.
When to Check and Change Automatic
Transmission Fluid
A good time to check your automatic transmission fluid
level is when the engine oil is changed.
Change the fluid and filter at the intervals listed in
Scheduled Maintenance on page 7-3, and be sure to
use the transmission fluid listed inRecommended Fluids
and Lubricants on page 7-12.
6-21