2005 GMC SIERRA light

If you will be pulling a trailer that, when loaded, will
weigh more than 5,000 lbs (2 270 kg) be sure to use a
properly mounted weight-distributing hitch and sway
control of the proper size. This equipment is very
important for proper vehicle loading and good handling
when driving. Always use a sway control if the trailer
will weigh more than these limits. You can ask a
hitch dealer about sway controls.
Fifth Wheel and Gooseneck Trailering
Fifth wheel and gooseneck trailers can be used
with many pickup models. These trailers place a
larger percentage of the weight (kingpin weight)
on the tow vehicle than conventional trailers. Make
sure this weight does not cause the vehicle to
exceed GAWR or GVWR.
Fifth wheel or gooseneck kingpin weight should be
15 to 25 percent of the trailer weight up to the maximum
amount specied in the trailering chart for your vehicle.
See “Weight of the Trailer” in this section for more
information.The hitch should be located in the pickup bed so that its
centerline is over or slightly in front of the rear axle.
Take care that it is not so far forward that it will contact
the back of the cab in sharp turns. This is especially
important for short box pickups. Trailer pin box
extensions and sliding fth wheel hitch assemblies can
help this condition. There should be at least
six inches of clearance between the top of the pickup
box and the bottom of the trailer shelf that extends over
the box.
Make sure the hitch is attached to the tow vehicle frame
rails. Do not use the pickup box for support.
4-86

Passing
You’ll need more passing distance up ahead when
you’re towing a trailer. And, because you’re a good deal
longer, you’ll need to go much farther beyond the
passed vehicle before you can return to your lane.
Backing Up
Hold the bottom of the steering wheel with one hand.
Then, to move the trailer to the left, just move that hand
to the left. To move the trailer to the right, move your
hand to the right. Always back up slowly and, if possible,
have someone guide you.
Making Turns
Notice:Making very sharp turns while trailering
could cause the trailer to come in contact with the
vehicle. Your vehicle could be damaged. Avoid
making very sharp turns while trailering.
When you’re turning with a trailer, make wider turns
than normal. Do this so your trailer won’t strike
soft shoulders, curbs, road signs, trees or other objects.
Avoid jerky or sudden maneuvers. Signal well in
advance.
Turn Signals When Towing a Trailer
The arrows on your instrument panel will ash whenever
you signal a turn or lane change. Properly hooked up,
the trailer lamps will also ash, telling other drivers
you’re about to turn, change lanes or stop.
When towing a trailer, the arrows on your instrument
panel will ash for turns even if the bulbs on the trailer
are burned out. Thus, you may think drivers behind
you are seeing your signal when they are not. It’s
important to check occasionally to be sure the trailer
bulbs are still working.
Driving On Grades
Reduce speed and shift to a lower gearbeforeyou start
down a long or steep downgrade. If you don’t shift
down, you might have to use your brakes so much that
they would get hot and no longer work well.
If you have an automatic transmission, you can tow in
DRIVE (D). You may want to shift the transmission
to a lower gear selection if the transmission shifts too
often (e.g., under heavy loads and/or hilly conditions).
You may also want to activate the tow/haul mode if
the transmission shifts too often. SeeTow/Haul Mode
Light on page 3-49.
4-89

Maintenance When Trailer Towing
Your vehicle will need service more often when you’re
pulling a trailer. SeeScheduled Maintenance on
page 6-4for more information. Things that are especially
important in trailer operation are automatic transmission
uid (don’t overll), engine oil, axle lubricant, belt,
cooling system and brake system. Each of these is
covered in this manual, and the Index will help you nd
them quickly. If you’re trailering, it’s a good idea to
review these sections before you start your trip.
Check periodically to see that all hitch nuts and bolts
are tight.
Trailer Wiring Harness
Your vehicle is equipped with one of the following wiring
harnesses for towing a trailer or hauling a slide-in
camper.
Basic Trailer Wiring
All regular, extended cab and crew cab pickups have an
eight-wire trailer towing harness.For vehicles not equipped with heavy duty trailering, the
harness is clipped to the vehicle’s frame behind the
spare tire mount. The harness requires the installation
of a trailer connector, which is available through
your dealer.
If your trailer is equipped with electric brakes, you can
get a jumper harness (electric trailer brake control)
with a trailer battery feed fuse from your dealer.
If you need to tow a light-duty trailer with a standard
four-way round pin connector, you can also get an
adapter form your dealer.
4-92

Heavy-DutyTrailer Wiring Harness
Package
For vehicles equipped with heavy duty trailering, the
harness is connected to the trailer plug mounted to the
hitch platform.The eight-wire harness contains the following trailer
circuits:
Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn Signal
Brown: Taillamps
White: Ground
Light Green: Back-up Lamps
Light Blue: CHMSL*
Red: Battery Feed**
Dark Blue: Trailer Brake
* The Center High-Mounted Stoplamp (CHMSL) wire is
tied next to the trailer wiring harness for use with a
trailer, slide-in camper or cap.
**If your vehicle is charging a remote (non-vehicle)
battery, turn on the headlamps to boost the vehicle
system voltage and properly charge the battery.
4-93

Camper/Fifth-Wheel Trailer Wiring Package
The eight-wire camper harness is located under the
front edge of the pickup box on the driver’s side of the
vehicle, attached to the frame bracket. A connector
will have to be added to the wiring harness which
connects to the camper.
The eight-wire harness contains the following
camper/trailer circuits:
Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn Signal
Brown: Taillamps
White: Ground
Light Green: Back-up Lamps
Light Blue: Center High-Mounted Stoplamp
(CHMSL)
Red: Battery Feed
Dark Blue: Trailer BrakeIf your vehicle is equipped with the “Heavy-Duty
Trailering” option, please refer to “Heavy-Duty Trailer
Wiring Package” earlier in this section.
When the camper-wiring harness is ordered without the
heavy-duty trailering package, an eight-wire harness
with a seven-pin connector and separate CHMSL
connector are located at the rear of the vehicle and are
tied to the vehicle’s frame.
4-94

Power Take-Off (PTO)
Before using a Power Take-Off (PTO), if equipped, refer
to the manufacturer’s or installer’s instructions.
To engage a PTO on a vehicle with a manual
transmission do the following:
1. Hold the clutch pedal down.
2. Set the parking brake.
3. Shift the transmission into NEUTRAL.
4. Engage the PTO. Refer to the manufacturer’s
or installer’s for instructions on electrically
engaged PTOs.
5. For mobile operations, shift the transmission into
the gear you want, apply the regular brakes and
release the parking brake. For stationary operations,
leave the parking brake applied.
6. Release the clutch and regular brakes as you
normally would. When the clutch is released,
the PTO will start.
7. Turn the PTO rotary switch to ON.To engage a PTO on a vehicle with an automatic
transmission do the following:
1. For stationary use shift the transmission into
PARK (P).
2. Turn the PTO rotary switch ON.
3. If the engine speed is below the PTO engage
speed limit, the PTO will start. The blinking LED
on the PTO control switch indicates PTO engage is
requested. When PTO engages the LED will
switch from blinking to a steady light.
To use PTO speed control in Preset Mode (Factory
Setting) do the following:
1. Engage the PTO.
2. Select PARK (P) or NEUTRAL (N) range. Apply the
parking brake if NEUTRAL (N) is selected. Torque
Converter Clutch (TCC) is not available in
NEUTRAL (N) and is available only in PARK (P)
when engine speed is above 1,100 rpm.
3. Make sure your foot is off the brake pedal (and off
the clutch on vehicles equipped with a manual
transmission).
4. Select the desired engine speed for PTO operation.
Read the following preset mode information
regarding operation.
4-98

Adding Equipment to the Outside
of Your Vehicle
Things you might add to the outside of your vehicle can
affect the airow around it. This may cause wind
noise and affect windshield washer performance. Check
with your dealer before adding equipment to the
outside of your vehicle.
Fuel
If your vehicle has a diesel engine, see “Diesel Fuel
Requirements and Fuel System” in the Diesel Engine
Supplement.
For vehicles with gasoline engines, please read this.
Gasoline Octane
For all except vehicles with the 6000 V8 (VIN Code N)
engine, use regular unleaded gasoline with a posted
octane of 87 or higher. If the octane is less than 87, you
may get a heavy knocking noise when you drive. If this
occurs, use a gasoline rated at 87 octane or higher as
soon as possible. Otherwise, you might damage your
engine. A little pinging noise when you accelerate or drive
uphill is considered normal. This does not indicate a
problem exists or that a higher-octane fuel is necessary.
If you are using 87 octane or higher-octane fuel and hear
heavy knocking, your engine needs service.
If you have the 6000 V8 (VIN Code N) engine, use
premium unleaded gasoline with a posted octane of
91 or higher for best performance. You may also
use middle grade or regular unleaded gasoline rated at
87 octane or higher, but your vehicle’s acceleration
may be slightly reduced. If the octane is less than 87,
you may get a heavy knocking noise when you drive.
If this occurs, use gasoline rated at 87 octane or higher
as soon as possible. Otherwise, you might damage
your engine.
5-6

Be careful not to spill fuel. Do not top off or overll the
tank and wait a few seconds after you have nished
pumping before removing the nozzle. Clean fuel
from painted surfaces as soon as possible. See
Washing Your Vehicle on page 5-116.
When replacing the fuel cap, turn it to the right
(clockwise) until it clicks. It will require more effort to
turn the fuel cap on the last turn as you tighten it. Make
sure the cap is fully installed. The diagnostic system
can determine if the fuel cap has been left off or
improperly installed. This would allow fuel to evaporate
into the atmosphere. SeeMalfunction Indicator Lamp
on page 3-44.
{CAUTION:
If a re starts while you are refueling, do not
remove the nozzle. Shut off the ow of fuel by
shutting off the pump or by notifying the
station attendant. Leave the area immediately.
Notice:If you need a new fuel cap, be sure to get
the right type. Your dealer can get one for you.
If you get the wrong type, it may not t properly.
This may cause your malfunction indicator lamp to
light and may damage your fuel tank and emissions
system. SeeMalfunction Indicator Lamp on
page 3-44.
5-11