brake light GMC SIERRA CLASSIC 2007 Owner's Manual

The hitch should be located in the pickup bed so
that it’s 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.
Safety Chains
You should always attach chains between your
vehicle and your trailer. Cross the safety chains
under the tongue of the trailer to help prevent the
tongue from contacting the road if it becomes
separated from the hitch. Instructions about safety
chains may be provided by the hitch manufacturer
or by the trailer manufacturer. If you are towing a
trailer up to 5,000 lbs (2 271 kg) with a
factory-installed step bumper, you may attach the
safety chains to the attaching points on the bumper.
If you are towing a trailer up to your vehicle’s trailer
rating limit you may attach the safety chains to the
attaching point on the hitch platform. If you aretowing with an aftermarket hitch follow the trailer or
hitch manufacturer’s recommendation for attaching
safety chains. Always leave just enough slack so
you can turn with your rig. Never allow safety
chains to drag on the ground.
Trailer Brakes
If your trailer weighs more than 2,000 lbs (900 kg)
loaded, then it needs its own brakes – and they
must be adequate. Be sure to read and follow the
instructions for the trailer brakes so you’ll be
able to install, adjust and maintain them properly.
Your trailer brake system can tap into the
vehicle’s hydraulic brake system only if:
The trailer parts can withstand 3,000 psi
(20 650 kPa) of pressure.
The trailer’s brake system will use less than
0.02 cubic inch (0.3 cc) of uid from your
vehicle’s master cylinder. Otherwise,
both braking systems won’t work well. You
could even lose your brakes.
If everything checks out this far, make the brake tap
at the port on the master cylinder that sends the
uid to the rear brakes. But don’t use copper tubing
for this. If you do, it will bend and nally break off.
Use steel brake tubing.
450

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.
453

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.
456

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.
457

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.
458

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.
461

Brake Wear
Your vehicle has front disc brakes and may have
rear drum brakes or rear disc brakes.
Disc brake pads have built-in wear indicators that
make a high-pitched warning sound when the
brake pads are worn and new pads are needed.
The sound may come and go or be heard all
the time your vehicle is moving, except when you
are pushing on the brake pedal rmly.
{CAUTION:
The brake wear warning sound means that
soon your brakes will not work well. That
could lead to an accident. When you hear
the brake wear warning sound, have your
vehicle serviced.
Notice:Continuing to drive with worn-out
brake pads could result in costly brake repair.
Some driving conditions or climates may cause
a brake squeal when the brakes are rst applied or
lightly applied. This does not mean something is
wrong with your brakes.Properly torqued wheel nuts are necessary to help
prevent brake pulsation. When tires are rotated,
inspect brake pads for wear and evenly tighten
wheel nuts in the proper sequence to GM torque
specications.
If you have rear drum brakes, they do not have
wear indicators, but if you ever hear a rear brake
rubbing noise, have the rear brake linings
inspected immediately. Rear brake drums should
be removed and inspected each time the tires
are removed for rotation or changing. Drum brakes
have an inspection hole to inspect lining wear
during scheduled maintenance. When you have
the front brake pads replaced, have the rear
brakes inspected, too.
Brake linings should always be replaced as
complete axle sets.
Brake Pedal Travel
See your dealer if the brake pedal does not return
to normal height, or if there is a rapid increase in
pedal travel. This could be a sign of brake trouble.
Brake Adjustment
Every time you make a brake stop, your brakes
adjust for wear.
519

3. Get the vehicles close enough so the jumper
cables can reach, but be sure the vehicles are
not touching each other. If they are, it could
cause a ground connection you do not
want. You would not be able to start your
vehicle, and the bad grounding could damage
the electrical systems.
To avoid the possibility of the vehicles rolling,
set the parking brake rmly on both vehicles
involved in the jump start procedure. Put
an automatic transmission in PARK (P) or a
manual transmission in NEUTRAL before
setting the parking brake. If you have a
four-wheel-drive vehicle, be sure the transfer
case is in a drive gear, not in NEUTRAL.Notice:If you leave your radio or other
accessories on during the jump starting
procedure, they could be damaged. The repairs
would not be covered by your warranty. Always
turn off your radio and other accessories when
jump starting your vehicle.
4. Turn off the ignition on both vehicles. Unplug
unnecessary accessories plugged into the
cigarette lighter or accessory power outlets.
Turn off the radio and all lamps that are
not needed. This will avoid sparks and help
save both batteries. And it could save
the radio!
522

(C) Aspect Ratio:A two-digit number that
indicates the tire height-to-width measurements.
For example, if the tire size aspect ratio is 75, as
shown in item C of the light truck (LT-Metric) tire
illustration, it would mean that the tire’s sidewall is
75 percent as high as it is wide.
(D) Construction Code:A letter code is used to
indicate the type of ply construction in the tire.
The letter R means radial ply construction;
the letter D means diagonal or bias ply
construction; and the letter B means belted-bias
ply construction.
(E) Rim Diameter:Diameter of the wheel in
inches.
(F) Service Description:The service description
indicates the load range and speed rating of a
tire. The load index can range from 1 to 279.
Speed ratings range from A to Z.Tire Terminology and Denitions
Air Pressure:The amount of air inside the tire
pressing outward on each square inch of the
tire. Air pressure is expressed in pounds
per square inch (psi) or kilopascal (kPa).
Accessory Weight:This means the combined
weight of optional accessories. Some examples of
optional accessories are, automatic transmission/
transaxle, power steering, power brakes, power
windows, power seats, and air conditioning.
Aspect Ratio:The relationship of a tire’s height
to its width.
Belt:A rubber coated layer of cords that is
located between the plies and the tread. Cords
may be made from steel or other reinforcing
materials.
Bead:The tire bead contains steel wires wrapped
by steel cords that hold the tire onto the rim.
Bias Ply Tire:A pneumatic tire in which the plies
are laid at alternate angles less than 90 degrees
to the centerline of the tread.
548

Fuses Usage
DRL Daytime Running Lamps
RVC Regulated Voltage Control
IPC/DICInstrument Panel
Cluster/Driver Information
Center
HVAC/ECAS Climate Control Controller
CIG LTR Cigarette Lighter
HI HDLP-RT High Beam Headlamp-Right
HDLP-LOW Headlamp Low Beam Relay
A/C COMPAir Conditioning Compressor
Relay
A/C COMP Air Conditioning Compressor
TCMB Transmission Control Module
RR WPR Not Used
RADIO Audio System
SEO B1Mid Bussed Electrical Center,
Rear Heated Seats,
Universal Home Remote
SystemFuses Usage
LO HDLP-LT Headlamp Low Beam-Left
BTSIBrake Transmission Shift
Interlock System
CRNK Starting System
LO HDLP-RT Headlamp Low Beam-Right
FOG LP Fog Lamps Relay
FOG LP Fog Lamps
HORN Horn Relay
W/S WASHWindshield Washer
Pump Relay
W/S WASH Windshield Washer Pump
INFOOnStar
®/Rear Seat
Entertainment
RADIO AMP Radio Amplier
RH HID Not Used
HORN Horn
EAP Not Used
TREC Not Used
607