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If Your Diesel Engine Will Not Start
If you have run out of fuel, seeRunning Out of Fuel on
page 5-17.
If you are not out of fuel, and your engine will not start,
do this:
Turn your ignition key to RUN. Immediately after the
wait to start light goes off, turn the ignition key to
START.
If the light does not go off, wait a few seconds, then try
starting your engine again. And, see your dealer as
soon as you can for a starting system check.
If the light comes on and then goes off and you know
your batteries are charged, but your engine still will not
start, your vehicle needs service.
If the light does not come on when the engine is cold,
your vehicle needs service.
If your batteries do not have enough charge to start
your engine, seeBattery on page 5-58.Be sure you have the right oil for your engine, and that
you have changed the oil at the proper times. If you
use the wrong oil, your engine may be harder to start.
Be sure you are using the proper fuel for existing
weather conditions. SeeWhat Fuel to Use on page 5-8.
If the engine starts, runs a short time, then stops,
your vehicle needs service.
{CAUTION:
Do not use gasoline or starting aids, such as
ether, in the air intake. They could damage
your engine. There could also be a re, which
could cause serious personal injury.
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•The charging system light should come on when
the ignition key is turned to RUN or START and
should go out when the engine is running above
idle. If the light does not go out or comes back on
during normal engine operation, have the charging
system checked right away. (This light tells you
if the generator is not charging; it does not reflect
the condition of the battery.) SeeCharging System
Light on page 3-31for more information.
•The voltmeter charge indicator gage tells you the
condition of your battery’s charge. The gage
should be in the center area during engine
operation. The red area on the left indicates an
undercharge condition; the red area on the
right indicates an overcharge. If the gage is in
either red area, have the battery and charging
system checked right away. SeeVoltmeter Gage
on page 3-32for more information.Notice:Do not allow the engine to operate at low
idle for more than ve minutes. This can cause
low engine operating temperatures which can affect
engine operation and reduce engine life. Engine
idle speed should be increased to 1200 rpm
whenever extended idle is required. Once started,
the engine should be placed under load to allow the
engine coolant temperature to reach 150°F (66°C)
before shutting off the engine.
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Page 126 of 398

Hazard Warning Flashers
The hazard warning flashers warn others. They also let
police know you have a problem. Your front and rear
turn signal lamps will flash on and off.
The hazard warning
flasher button is
located on top of the
steering column.
The hazard warning flashers work no matter what
ignition position the key is in, and even if the key is not
in the ignition.
Press the button to make the front and rear turn signal
lamps flash on and off. Press the button again to
turn the flashers off.
When the hazard warning flashers are on, your turn
signals will not work.
Other Warning Devices
If you carry reflective triangles, you can set them up at
the side of the road about 300 feet (100 m) behind
your vehicle.
Horn
Sound the horn by pushing the center of the steering
wheel. If you have the optional air horn, it is controlled
by a cord that you will find up above and to the left
of the driver. The harder you pull on the cord, the louder
the air horn will sound. The air horn works only after
your air brake system pressure gets up to about 115 psi
(790 kPa). The air horn will work properly unless the
air brake system pressure drops below 60 psi (415 kPa).
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Page 148 of 398

Engine Speed Limiter
All engines have electronic engine speed limiting.
The engine limited speeds range between
2,900 and 4,400 rpm depending on engine
option content.
Engine Road Speed Governor
This system controls maximum vehicle speed
automatically and reduces engine power until vehicle
speed gets down to maximum governed speed.
The default setting for C4500 and C5500 models up to
19,500 lbs GVWR is 80 to 85 mph (128 to 136 km/h).
Most other models have a default setting of 75 mph
(120 km/h), although some tire sizes and tread patterns
may limit maximum speed to 55 to 65 mph (86 to
105 km/h). You may have a label on the headliner of your
vehicle with more information on your engine road speed
governor. See your GM dealer for assistance with
programming your engine limited speed.
Safety Belt Reminder Light
When the key is turned to RUN or START, a light will
come on for several seconds to remind people to fasten
their safety belts.
The safety belt light will
also come on and stay on
for several seconds.
Safety Belt Reminder Tone
If your vehicle has this feature, when you turn your key
to RUN or START, a tone will sound for several
seconds to remind people to fasten their safety belts.
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Page 149 of 398

Airbag Readiness Light
If your vehicle has airbags, there is an airbag readiness
light on the instrument panel, which shows the airbag
symbol. The system checks the airbag’s electrical
system for malfunctions. The light tells you if there is an
electrical problem. The system check includes the
airbag sensors, the airbag modules, the wiring, the
passenger airbag suppression circuit and the crash
sensing and diagnostic module. For more information on
the airbag system, seeAirbag System on page 1-50.
This light will come on
when you start your
vehicle, and it will flash for
a few seconds. Then the
light should go out. This
means the system is ready.
If the airbag readiness light stays on after you start the
vehicle or comes on when you are driving, your
airbag system may not work properly. Have your vehicle
serviced right away.The airbag readiness light should flash for a
few seconds when you turn the ignition key to RUN or
START. If the light doesn’t come on then, have it
fixed so it will be ready to warn you if there is a problem.
{CAUTION:
If the airbag readiness light stays on after you
start your vehicle, it means the airbag system
may not be working properly. The airbags in
your vehicle may not in ate in a crash, or they
could even in ate without a crash. To help
avoid injury to yourself or others, have your
vehicle serviced right away if the airbag
readiness light stays on after you start your
vehicle.
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When the warning light comes on while you are driving,
you should drive only as far as the nearest point of
safety and then stop the vehicle. Here’s a very important
thing for you to know:
{CAUTION:
If the air brake system warning light comes on
and the warning tone sounds, the vehicle can
stop suddenly and without further warning.
This is because the parking brake will come on
if the pressure falls below 35 to 45 psi (240 to
310 kPa). You or others could be injured. If the
air brake system warning light comes on and
the warning tone sounds, stop as soon as you
can. You will not know how quickly the system
is losing pressure, so be aware that the
parking brake may come on suddenly.
Anti-Lock Brake System
Warning Light
This light will come on
briefly when you start your
engine, then it will turn
off. This is normal.
If the light stays on, or comes on when you are driving,
your vehicle needs service. If the BRAKE or LOW
AIR warning light is not on, you still have brakes, but
you do not have the anti-lock brake feature. If the
BRAKE and/or LOW AIR warning light is on, you do not
have anti-lock brakes and there is a problem with
your regular brakes. SeeBrake System Warning Light
on page 3-33andAnti-Lock Brake System (ABS)
on page 4-8for more information.
The anti-lock brake system warning light should come
on briefly when you turn the ignition key to ON. If
the light does not come on then, have it fixed so it will
be ready to warn you if there is a problem.
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Page 157 of 398

Low Coolant Warning Light
You have a low coolant
warning light. If this light
comes on, your system is
low on coolant and the
engine may overheat.
The warning light should come on briefly, as a check,
when you turn on the ignition.
When it comes on, you will also hear a warning tone at
several beats per second for 10 seconds. SeeEngine
Coolant (Gas and DURAMAX
®Engines) on page 5-38
orEngine Coolant (Caterpillar®Diesel Engines) on
page 5-40and have your vehicle serviced as soon as
you can.
This light may also come on if your vehicle is equipped
with the automatic engine shutdown system and
engine shutdown has begun. SeeEngine Alarm and
Automatic ShutdownunderStarting the Diesel Engine
on page 2-15.
Wait to Start Indicator
(Diesel Engine)
If your vehicle has the DURAMAX®6.6L diesel engine,
you will have glow plugs and an air intake heater. If
your vehicle has the DURAMAX
®7.8L diesel engine,
you will have glow plugs and an inlet heater. If your
vehicle has a Caterpillar
®engine, you will have an
inlet heater.
The light in the center of
the instrument panel will
come on when the
inlet heater or glow plugs
are on and the ignition
key is in RUN.
Wait until the indicator light turns off before turning the
ignition key to START.
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Page 192 of 398

According to the American Medical Association, a 180 lb
(82 kg) person who drinks three 12 ounce (355 ml)
bottles of beer in an hour will end up with a BAC
of about 0.06 percent. The person would reach the
same BAC by drinking three 4 ounce (120 ml) glasses
of wine or three mixed drinks if each had 1-1/2 ounces
(45 ml) of liquors like whiskey, gin, or vodka.It is the amount of alcohol that counts. For example, if
the same person drank three double martinis (3 ounces
or 90 ml of liquor each) within an hour, the person’s
BAC would be close to 0.12 percent. A person
who consumes food just before or during drinking will
have a somewhat lower BAC level.
There is a gender difference, too. Women generally
have a lower relative percentage of body water
than men. Since alcohol is carried in body water, this
means that a woman generally will reach a higher BAC
level than a man of her same body weight will when
each has the same number of drinks.
The law in most U.S. states, and throughout Canada,
sets the legal limit at 0.08 percent. In some other
countries, the limit is even lower. For example, it is
0.05 percent in both France and Germany. The
BAC limit for all commercial drivers in the United States
is 0.04 percent.
The BAC will be over 0.10 percent after three to
six drinks (in one hour). Of course, as we have seen, it
depends on how much alcohol is in the drinks, and
how quickly the person drinks them.
4-4