2001 GMC SIERRA brake

4-80
If your vehicle is equipped with the ªHeavy-Duty
Traileringº option, please refer to ªHeavy
-Duty Trailer
Wiring Packageº, 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.Instrument Panel Jumper Wiring Harness
This harness is included with the heavy-duty and
camper/fifth
-wheel trailer wiring packages. The harness
is for an electric trailer brake controller and includes a
trailer battery feed fuse. This harness and fuse should be
installed by your dealer or a qualified service center.

4-81 Auxiliary Battery (If Equipped)
The auxiliary battery provision can be used to supply
electrical power to additional equipment that you may
choose to add, such as a slide
-in camper.
If your vehicle has this
provision, this relay will be
located on the passenger's
side of the vehicle, next to
the auxiliary battery.
When using this provision, connection should only be
made to the upper stud (A) of the relay. Do not make
connections to the lower stud (B) of the relay.
The auxiliary battery circuit is protected by a megafuse
located behind the auxiliary battery.
Be sure to follow the proper installation instructions that
are included with any electrical equipment that you install.
NOTICE:
When using the auxiliary battery provision, the
electrical load must not exceed 30 amps. Always
turn off any electrical equipment when not in use.
Leaving electrical equipment on for extended
periods will drain your battery.
Power Winches
If you wish to use a power winch on your vehicle, only
use it when your vehicle is stationary or anchored.
NOTICE:
Using a power winch with the transmission in
gear may damage the transmission. When
operating a power winch, always leave the
transmission in NEUTRAL (N).
Use the regular brakes, set the parking brake, or block
the wheels to keep your vehicle from rolling.

4-82 Power Take-Off (PTO) (If Equipped)
NOTICE:
If you have a PTO that will exceed 35 hp installed on
your vehicle, it could damage the transfer case or
transmission. When having a PTO installed on your
vehicle, make sure that it will not exceed 35 hp.
Before using a PTO, refer to the manufacturer's or
installer's instructions.
NOTICE:
Using a PTO while operating in one place before
the vehicle has reached normal operating
temperature can damage the transfer case or
transmission. If you will be using the PTO while
operating in one place, drive and warm up the
vehicle before using the PTO.
To engage a PTO on a vehicle with a
manual transmission:
1. Hold the clutch pedal down.
2. Set the parking brake.
3. Shift the transmission into NEUTRAL (N).
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:
1. Engine speed must be less than 1000 rpm.
2. Turn the PTO rotary switch ON.

4-83
Using PTO speed control in Preset Mode
(Factory Setting):
1. Engage the PTO.
2. Select PARK (P) or NEUTRAL (N) range.
Apply the parking brake in NEUTRAL (N) is
selected. Torque Converter Clutch (TCC) lockup is
not available in NEUTRAL (N) and is available only
in PARK when engine speed is above 1100 rpm.
3. Make sure your foot is off the brake pedal
(and off the clutch on vehicles equipped with a
manual transmission). Select the desired engine
speed for PTO operation. Please read the following
Preset Mode information regarding operation.
Preset Mode: PTO speed control mode is used for
stationary applications. This mode provides a default
standby speed of 800 or 850 rpm (depending on the
engine/transmission combination) and two default PTO
control speeds which follow:

PTO Fast Idle Speed of 1250 rpm, or

PTO Fast Idle Resume Speed of 1700 rpm.
Standby speed (800/850 rpm) is not to be used as a
PTO control speed. Vehicles not equipped with cruise
control will not have the resume speed capability.Using PTO speed control in Variable Mode (Mobile):
1. Engage the PTO.
2. Vehicle speed must be greater than 5 mph for vehicles
equipped with gasoline engines or greater than 0 mph
for vehicles equipped with diesel engines.
3. Make sure your foot is off the brake pedal
(and off the clutch for vehicles equipped with a
manual transmission).
4. Select the desired engine speed (with the foot pedal)
and select SET on the PTO switch or with the
cruise control.
Using PTO speed control in Variable
Mode (Stationary):
1. Engage the PTO.
2. Vehicle speed must be less than 5 mph for vehicles
equipped with gasoline engines or at 0 mph for
vehicles equipped with diesel engines.
3. Make sure your foot is off the brake pedal
(and off the clutch for vehicles equipped with a
manual transmission).
4. Select the desired engine speed (with the foot pedal)
and select SET on the PTO switch or with the
cruise control.

5-4
2. Get the vehicles close enough so the jumper cables
can reach, but be sure the vehicles aren't touching
each other. If they are, it could cause a ground
connection you don't want. You wouldn't 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 firmly on both vehicles involved in the
jump start procedure. Put an automatic transmission in
PARK (P) or a manual transmission in NEUTRAL (N).
If you have a four
-wheel-drive vehicle, be sure the
transfer case is not in NEUTRAL (N).
3. Turn off the ignition on both vehicles. Unplug
unnecessary accessories plugged into the cigarette
lighter or accessory power outlets. Turn off all lamps
that aren't needed as well as radios. This will avoid
sparks and help save both batteries. In addition,
it could save your radio!
NOTICE:
If you leave your radio on, it could be badly
damaged. The repairs wouldn't be covered by
your warranty.
4. Open the hoods and locate the positive (+) and
negative (
-) terminal locations on the other vehicle.
Your vehicle has a remote positive (+) jump starting
terminal and a remote negative (
-) jump starting
terminal. The remote positive (+) terminal is located
behind a red plastic cover near the engine accessory
drive bracket. To uncover the remote positive (+)
terminal, open the red plastic cover.
On all V8 gasoline and diesel engines, the remote
negative (
-) terminal is located on the engine
accessory drive bracket. This is marked ªGNDº on
V8 engines. On V6 engines, the remote negative (
-)
terminal is located on a tab attached to the engine
accessory drive bracket where it is marked ªGNDº.
You should always use the remote positive (+)
and the remote negative (
-) terminals instead of
the positive (+) and negative (
-) terminals on
your battery.

5-18
Engine Fan Noise
Your vehicle has a clutched engine cooling fan. When
the clutch is engaged, the fan spins faster to provide
more air to cool the engine. In most everyday driving
conditions, the fan is spinning slower and the clutch is
not fully engaged. This improves fuel economy and
reduces fan noise. Under heavy vehicle loading, trailer
towing and/or high outside temperatures, the fan speed
increases as the clutch more fully engages. So you may
hear an increase in fan noise. This is normal and should
not be mistaken as the transmission slipping or making
extra shifts. It is merely the cooling system functioning
properly. The fan will slow down when additional
cooling is not required and the clutch disengages.
You may also hear this fan noise when you start
the engine. It will go away as the fan clutch
partially disengages.
If a Tire Goes Flat
It's unusual for a tire to ªblow outº while you're driving,
especially if you maintain your tires properly. If air goes
out of a tire, it's much more likely to leak out slowly.
But if you should ever have a ªblowout,º here are a
few tips about what to expect and what to do:
If a front tire fails, the flat tire will create a drag that
pulls the vehicle toward that side. Take your foot off
the accelerator pedal and grip the steering wheel firmly.
Steer to maintain lane position, and then gently brake to
a stop well out of the traffic lane.
A rear blowout, particularly on a curve, acts much like a
skid and may require the same correction you'd use in
a skid. In any rear blowout, remove your foot from
the accelerator pedal. Get the vehicle under control by
steering the way you want the vehicle to go. It may be
very bumpy and noisy, but you can still steer. Gently
brake to a stop
-- well off the road if possible.
If a tire goes flat, the next part shows how to use your
jacking equipment to change a flat tire safely.

5-19
Changing a Flat Tire
If a tire goes flat, avoid further tire and wheel damage
by driving slowly to a level place. Turn on your hazard
warning flashers.
CAUTION:
Changing a tire can cause an injury. The vehicle
can slip off the jack and roll over you or other
people. You and they could be badly injured.
Find a level place to change your tire. To help
prevent the vehicle from moving:
1. Set the parking brake firmly.
2. Put an automatic transmission shift lever in
PARK (P) or shift a manual transmission
to FIRST (1) or REVERSE (R).
3. If you have a four
-wheel-drive vehicle,
be sure the transfer case is in a drive
gear
-- not in NEUTRAL.
CAUTION: (Continued)
CAUTION: (Continued)
4. Turn off the engine.
5. Put the wheel blocks at the front and rear
of the tire farthest away from the one being
changed. That would be the tire on the other
side of the vehicle, at the opposite end.
The following steps will tell you how to use the jack and
change a tire.

5-31
CAUTION:
Incorrect wheel nuts or improperly tightened
wheel nuts can cause the wheel to become loose
and even come off. This could lead to an accident.
Be sure to use the correct wheel nuts. If you have
to replace them, be sure to get new GM original
equipment wheel nuts.
Stop somewhere as soon as you can and have the
nuts tightened with a torque wrench to the proper
torque. See ªCapacities and Specificationsº in
the Index.
NOTICE:
Improperly tightened wheel nuts can lead to
brake pulsation and rotor damage. To avoid
expensive brake repairs, evenly tighten the wheel
nuts in the proper sequence and to the proper
torque specification.
Storing a Flat or Spare Tire and Tools
CAUTION:
Storing a jack, a tire or other equipment in the
passenger compartment of the vehicle could
cause injury. In a sudden stop or collision, loose
equipment could strike someone. Store all these
in the proper place.