2007 GMC SIERRA CLASSIC light

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 gearbefore
you 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 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 264.
If you have a 5-speed manual transmission and
you are towing a trailer, it’s better not to use
FIFTH (5) gear. Just drive in FOURTH (4) gear
(or, as you need to, a lower gear).
When towing at high altitude on steep uphill
grades, consider the following: Engine coolant at
or near sea level will boil at a lower temperature
than at higher altitudes. If you turn your engine off
immediately after towing at high altitude on
steep uphill grades, your 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
PARK (P) for a few minutes before turning
the engine off. For manual transmissions, let the
engine run while parked, preferably on level
ground, with the transmission out of gear and the
parking brake applied, for a few minutes before
turning the engine off. If you do get the overheat
warning, seeEngine Overheating on page 505.
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Maintenance When Trailer Towing
Your vehicle will need service more often when
you’re pulling a trailer. SeeScheduled
Maintenance (Gasoline Engine) on page 617for
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 from your dealer.
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Heavy-DutyTrailer Wiring Harness
Package
For vehicles equipped with heavy duty trailering,
the harness is connected to the trailer 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 you are charging a remote (non-vehicle)
battery, press the tow/haul mode button located at
the end of the shift lever. This will boost the
vehicle system voltage and properly charge the
battery. If the trailer is too light for tow/haul mode,
you can turn on the headlamps as a second
way to boost the vehicle system voltage and
charge the battery.
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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.
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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.
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If your vehicle has the 6.0L V8 engine
(VIN Code N), use premium unleaded gasoline
with a posted octane rating of 91 or higher.
You may also use regular unleaded gasoline rated
at 87 octane or higher, but your vehicle’s
acceleration may be slightly reduced, and you
may notice a slight audible knocking noise,
commonly referred to as spark knock. If the octane
is less than 87, you may notice 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. If you are using gasoline rated at
87 octane or higher and you hear heavy knocking,
your engine needs service.
Gasoline Specications
At a minimum, gasoline should meet ASTM
specication D 4814 in the United States or
CAN/CGSB-3.5 in Canada. Some gasolines may
contain an octane-enhancing additive called
methylcyclopentadienyl manganese tricarbonyl
(MMT). General Motors recommends against the
use of gasolines containing MMT. SeeAdditives
on page 472for additional information.
California Fuel
If your vehicle is certied to meet California
Emissions Standards, it is designed to operate on
fuels that meet California specications. See the
underhood emission control label. If this fuel is not
available in states adopting California emissions
standards, your vehicle will operate satisfactorily on
fuels meeting federal specications, but emission
control system performance may be affected. The
malfunction indicator lamp may turn on and your
vehicle may fail a smog-check test. SeeMalfunction
Indicator Lamp on page 258. If this occurs, return to
your authorized GM dealer for diagnosis. If it is
determined that the condition is caused by the type
of fuel used, repairs may not be covered by your
warranty.
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When replacing the fuel cap, turn it 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 258.
The TIGHTEN FUEL CAP message will be
displayed on the Driver Information Center (DIC) if
the fuel cap is not properly installed. SeeDIC
Warnings and Messages on page 270for more
information.
{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. See
Malfunction Indicator Lamp on page 258.
476

Engine Oil (Gasoline Engine)
If your vehicle has a diesel engine, see “Engine
Oil” in the DURAMAX®Diesel Engine Supplement.
If the CHECK OIL LEVEL light appears on the
instrument cluster, except vehicles that have the
4.3L engine, it means you need to check the
engine oil level right away.
For more information, seeDriver Information
Center (DIC) on page 265. You should check
your engine oil level regularly; this is an added
reminder.
Checking Engine Oil
It is a good idea to check the engine oil every time
you get fuel. 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 480
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 you
do not do this, 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.
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