trailer GMC SIERRA 2001 Service Manual

4-77 When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal down
while you:

Start your 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
Your vehicle will need service more often when you're
pulling a trailer. See the Maintenance Schedule for
more on this. Things that are especially important
in trailer operation are automatic transmission fluid
(don't overfill), engine oil, axle lubricant, belt, cooling
system and brake system. Each of these is covered in
this manual, and the Index will help you find 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 Package
All regular, extended cab crew cab pickups have a
six
-wire trailer towing harness.
The six-wire harness is located at the rear of the vehicle
and is tied to the vehicle's frame. The harness requires
the installation of a trailer
-wiring harness connector,
which is available through your dealer.

4-78
The six-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: Center High
-Mounted
Stoplamp (CHMSL)
If you need to upgrade your vehicle to heavy
-duty
trailering, a brake controller harness and an underbody
harness with a seven
-pin universal heavy-duty trailer
connector are available from your dealer.Heavy
-Duty Trailer Wiring Package (If Equipped)
Your pickup may be equipped with the eight-wire trailer
towing harness. This harness with a seven
-pin universal
heavy
-duty trailer connector is attached to a bracket on
the platform hitch.*
* 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.

4-79
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
A jumper harness for an electric trailer brake controller
and a trailer battery feed fuse are included with this
trailering package. (See ªInstrument Panel Jumper
Wiring Harnessº later in this section.)
If you need to tow a light
-duty trailer with a standard
four
-way round pin connector, an adapter connector is
available from your dealer.Camper/Fifth
-Wheel Trailer Wiring Package
(If Equipped)
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 Brake
A jumper harness for an electric trailer brake controller
and a trailer battery feed fuse are included with this
trailering package. (See ªInstrument Panel Jumper
Wiring Harnessº later in this section.)

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.

4-84
Variable Mode: PTO speed control mode can be used
for both stationary and mobile applications. This mode
allows PTO to be controlled in a fashion similar to how
cruise control sets vehicle speed. The operator can set to
an rpm (between 800 and 2200) with the cruise control
feature or with the SET position on the PTO switch.
The operator is then able to increase engine speed in
100 rpm increments with the resume position on the
cruise control. The operator can also decrease engine
speed in 100 rpm increments with either the SET
position on the cruise control or the PTO switch.
Vehicles not equipped with cruise control will not
have the resume capability.
All engine speed values listed above are factory preset
values. With the exception of the TCC lockup speed
(1100 rpm) and the ªtapº increment (100 rpm), all of
these values are programmable and can be adjusted by
your GM dealer or body upfitter. If the PTO software
settings do not match the settings shown here, then
they may have already been altered in order to satisfy
the requirements of the installed PTO system and
body equipment.Step-Bumper Pad
If your vehicle has a rear step bumper, it may be
equipped with a rear step pad at the center of
the bumper.
If you will be using the
bumper to tow a trailer,
you must remove the
center cutout circle to
install the trailer ball.

5-8
1. Disconnect the black negative (-) cable from the
heavy, unpainted metal engine part on the vehicle
that had the dead battery.
2. Disconnect the black negative (
-) cable from the
negative (
-) terminal on the vehicle with the
good battery.
3. Disconnect the red positive (+) cable from the
vehicle with the good battery.
4. Disconnect the red positive (+) cable from the
other vehicle.
Towing Your Vehicle
Consult your dealer or a professional towing service if
you need to have your vehicle towed. See ªRoadside
Assistanceº in the Index.
Engine Overheating
You will find a coolant temperature gage on your
vehicle's instrument panel. See ªEngine Coolant
Temperature Gageº in the Index. In addition,
you will find a LOW COOLANT, CHECK COOLANT
TEMP, ENGINE OVERHEATED and a REDUCED
ENGINE POWER message in the message center on the
instrument panel. See ªMessage Centerº in the Index.
Overheated Engine Protection Operating
Mode (V8 Engines Only)
Should an overheated engine condition exist and the
REDUCED ENGINE POWER message is displayed,
an overheat protection mode which alternates firing
groups of cylinders helps prevent engine damage.
In this mode, you will notice a loss in power and
engine performance. This operating mode allows your
vehicle to be driven to a safe place in an emergency.
Towing a trailer in the overheat protection mode
should be avoided.
NOTICE:
After driving in the overheated engine protection
operating mode, to avoid engine damage, allow
the engine to cool before attempting any repair.
The engine oil will be severely degraded. Repair
the cause of coolant loss, change the oil and reset
the oil life monitor. See ªEngine Oilº in the Index.

5-10 If No Steam Is Coming From Your Engine
If you get an engine overheat warning but see or hear no
steam, the problem may not be too serious. Sometimes
the engine can get a little too hot when you:

Climb a long hill on a hot day.

Stop after high
-speed driving.

Idle for long periods in traffic.

Tow a trailer. See ªDriving on Gradesº in the Index.
If you get the overheat warning with no sign of steam,
try this for a minute or so:
1. If you have an air conditioner and it's on, turn it off.
2. Turn on your heater to full hot at the highest fan
speed and open the window as necessary.
3. If you're in a traffic jam, shift to NEUTRAL (N);
otherwise, shift to the highest gear while
driving
-- DRIVE (D) for automatic transmissions.If you no longer have the overheat warning, you
can drive. Just to be safe, drive slower for about
10 minutes. If the warning doesn't come back on,
you can drive normally.
If the warning continues, pull over, stop, and park
your vehicle right away.
If there's still no sign of steam, push down the
accelerator until the engine speed is about twice as fast
as normal idle speed for at least three minutes while
you're parked. If you still have the warning, turn off
the engine and get everyone out of the vehicle until it
cools down. Also, see ªOverheated Engine Protection
Operating Modeº listed previously in this section.
You may decide not to lift the hood but to get service
help right away.

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.

6-21
3. Remove the air filter by pulling downward on the
element. Remove the second portion of the air filter
by sliding it towards the rear of the vehicle and then
pulling downward.
4. Install the new filter by reversing the steps listed
previously. Be sure to follow any instructions that
may be included in the replacement filter package.
Because this procedure can be a little difficult,
you may choose to have it done at your dealer's
service department.
Refer to the Maintenance Schedule to determine
when to replace the passenger compartment air filter.
See ªScheduled Maintenanceº in the Index.Automatic Transmission Fluid
(Except Allison Transmission)
When to Check and Change
A good time to check your automatic transmission fluid
level is when the engine oil is changed.
Change both the fluid and filter every 50,000 miles
(83 000 km) if the vehicle's GVWR is over 8,600 or
if the vehicle is mainly driven under one or more of
these conditions:

In heavy city traffic where the outside temperature
regularly reaches 90F (32C) or higher.

In hilly or mountainous terrain.

When doing frequent trailer towing.

Uses such as found in taxi, police or delivery service.
If you do not use your vehicle under any of
these conditions, change the fluid and filter every
100,000 miles (166 000 km).
See ªScheduled Maintenance Servicesº in the Index.

6-22 How to Check
Because this operation can be a little difficult,
you may choose to have this done at the dealership
service department.
If you do it yourself, be sure to follow all the instructions
here, or you could get a false reading on the dipstick.
NOTICE:
Too much or too little fluid can damage your
transmission. Too much can mean that some of
the fluid could come out and fall on hot engine
parts or exhaust system parts, starting a fire.
Be sure to get an accurate reading if you check
your transmission fluid.
Wait at least 30 minutes before checking the
transmission fluid level if you have been driving:

When outside temperatures are above 90F (32C).

At high speed for quite a while.
In heavy traffic
-- especially in hot weather.

While pulling a trailer.
To get the right reading, the fluid should be at normal
operating temperature, which is 180F to 200F
(82C to 93C).
Get the vehicle warmed up by driving about
15 miles (24 km) when outside temperatures are above
50F (10C). If it's colder than 50F (10C), drive
the vehicle in THIRD (3) until the engine temperature
gage moves and then remains steady for 10 minutes.
A cold fluid check can be made after the vehicle has
been sitting for eight hours or more with the engine off,
but this is used only as a reference. Let the engine run
at idle for five minutes if outside temperatures are
50F (10C) or more. If it's colder than 50F (10C),
you may have to idle the engine longer. Should the fluid
level be low during this cold check, you must check the
fluid hot before adding fluid. Checking the fluid hot will
give you a more accurate reading of the fluid level.