2004 GMC SIERRA turn signal

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 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. See
Tow/Haul Mode
Light on page 3-53.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).
If you have a 6-speed manual transmission and you are
towing a trailer, it's better not to use SIXTH (6) gear.
Drive in FIFTH (5) gear (or, as you need to, a lower gear).
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant will boil at a lower
temperature than at normal 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, see
Engine Overheating on page 5-36.
4-93

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 trailer wiring harness, an
additional 2±wire harness and 7 pin universal trailer
connector are available from your dealer.
Heavy-DutyTrailer Wiring Harness
Package
Your pickup may be equipped with the eight-wire trailer
towing harness. This harness with a seven-pin
universal trailer connector is attached to a bracket on
the hitch platform.
* 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.
4-96

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
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.
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 Brake
4-97

Service............................................................5-3
Doing Your Own Service Work.........................5-3
Adding Equipment to the Outside of Your
Vehicle......................................................5-4
Fuel................................................................5-4
Gasoline Octane............................................5-4
Gasoline Speci®cations....................................5-5
California Fuel...............................................5-5
Additives.......................................................5-6
Fuels in Foreign Countries...............................5-6
Filling Your Tank............................................5-7
Filling a Portable Fuel Container.......................5-9
Checking Things Under the Hood....................5-10
Hood Release..............................................5-10
Engine Compartment Overview.......................5-12
Engine Oil...................................................5-18
Engine Air Cleaner/Filter................................5-23
Automatic Transmission Fluid (Except Allison
Transmission
ž) ..........................................5-25
Automatic Transmission Fluid (Allison
Transmission
ž) ..........................................5-28
Manual Transmission Fluid.............................5-31
Hydraulic Clutch...........................................5-32
Engine Coolant.............................................5-33
Coolant Surge Tank Pressure Cap..................5-36
Engine Overheating.......................................5-36Cooling System............................................5-39
Engine Fan Noise.........................................5-44
Power Steering Fluid.....................................5-45
Windshield Washer Fluid................................5-46
Brakes........................................................5-48
Battery........................................................5-52
Jump Starting...............................................5-53
Rear Axle.......................................................5-59
Four-Wheel Drive............................................5-60
Noise Control System.....................................5-62
Tampering with Noise Control System
Prohibited.................................................5-62
Bulb Replacement..........................................5-64
Halogen Bulbs..............................................5-64
Headlamps..................................................5-64
Front Turn Signal, Sidemarker and Daytime
Running Lamps.........................................5-66
Roof Marker Lamps......................................5-67
Center High-Mounted Stoplamp (CHMSL) and
Cargo Lamp.............................................5-69
Pickup Box Identi®cation and Fender Marker
Lamps.....................................................5-70
Taillamps.....................................................5-71
Replacement Bulbs.......................................5-74
Section 5 Service and Appearance Care
5-1

Front Turn Signal, Sidemarker and
Daytime Running Lamps
A. Sidemarker Lamp
B. Retainer Clip
C. Front Turn Signal Lamp
D. Daytime Running Lamp1. Remove the headlamp assembly as mentioned
previously.
2. Press the retainer clip, located behind the turn
signal housing, towards the outside of the vehicle.
3. Pull the turn signal housing out from the vehicle.
4. Press the locking release lever, turn the bulb socket
counterclockwise and remove the socket from the
turn signal housing.
5. Remove the old bulb from the bulb socket.
6. Put the new bulb into the bulb socket. Use care not
to touch the bulb with your ®ngers or hands.
7. Put the bulb socket into the turn signal housing and
turn it clockwise until it locks.
8. Reinstall the turn signal housing onto the vehicle,
placing the hook and posts on the inner side into
the alignment holes, and the outer side into
the retainer bracket. Push until you hear a click.
9. Reinstall the headlamp assembly.
5-66

Taillamps
1. Open the tailgate.
2. Remove the two rear
lamp assembly screws
near the tailgate
latch and pull out the
lamp assembly.
Your vehicle may have
one of the following
taillamp assemblies:A. Stoplamp
B. Turn Signal
C. Back-up Lamp
5-71

A. Stoplamp
B. Turn Signal Lamp
C. Back-up Lamp
D. Side Marker Lamp
3. Press the release tab,
if equipped, and turn
the bulb socket
counterclockwise to
remove it from
the taillamp housing.
5-72

4. Pull the old bulb straight out from the socket.
5. Press a new bulb into the socket and turn the socket
clockwise into the taillamp housing.
6. Reinstall the rear lamp assembly.
7. Close the tailgate.
Taillamps (Chassis Cab Models)
A. Turn Signal Lamp
B. Stoplamp
C. Back-up Lamp1. Using your hands, peel the rubber seal away from
the lens.
2. Lift the lens off the lamp assembly.
3. Pull the old bulb straight out from the socket.
4. Put a new bulb into the socket and press it in until it
is tight.
5. Reinstall the lens and the lens seal.
5-73