2004 GMC SIERRA DENALI check engine

Testing the Alarm
The alarm can be tested by following these steps:
1. From inside the vehicle, lower the driver's window
and open the driver's door.
2. Activate the system by locking the doors with the
power door lock switch while the door is open, or
with the remote keyless entry transmitter.
3. Get out of the vehicle, close the door and wait for
the security message to go out.
4. Then reach in through the window, unlock the door
with the manual door lock and open the door. This
should set off the alarm.
If the alarm does not sound and the headlamps do not
¯ash, you may have the feature turned off. See
DIC
Operation and Displays on page 3-46for more
information.
Passlockž
Your vehicle is equipped with the
Passlockžtheft-deterrent system.
Passlock
žis a passive theft-deterrent system.
Passlockženables fuel if the ignition lock cylinder is
turned with a valid key. If a correct key is not used or the
ignition lock cylinder is tampered with, fuel is disabled.
If the engine stalls and the security light ¯ashes,
wait until the light stops ¯ashing before trying to restart
the engine. Remember to release the key from
START as soon as the engine starts.
If the engine is running and the security light comes on,
you will be able to restart the engine if you turn the
engine off. However, your Passlock
žsystem is
not working properly and must be serviced by your
dealer. Your vehicle is not protected by Passlock
žat this
time. You may also want to check the fuse. See
Fuses and Circuit Breakers on page 5-105. See your
dealer for service.
In an emergency, call the GM Roadside Assistance
Center. See
Roadside Assistance Program on page 7-6.
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When starting your engine in very cold weather
(below 0ÉF or-18ÉC), do this:
1. With your foot off the accelerator pedal, turn the
ignition key to START and hold it there up to
15 seconds. When the engine starts, let go of
the key.
2. If your engine still won't start (or starts but then
stops), it could be ¯ooded with too much gasoline.
Try pushing your accelerator pedal all the way to the
¯oor and holding it there as you hold the key in
START for about three seconds. When the engine
starts, let go of the key and accelerator. If the
vehicle starts brie¯y but then stops again, do the
same thing, but this time keep the pedal down
for ®ve or six seconds. This clears the extra
gasoline from the engine.
Notice:Your engine is designed to work with the
electronics in your vehicle. If you add electrical
parts or accessories, you could change the way the
engine operates. Before adding electrical equipment,
check with your dealer. If you do not, your engine
might not perform properly.
Engine Coolant Heater
In very cold weather, 0ÉF
(-18ÉC) or colder, the
engine coolant heater can
help. You'll get easier
starting and better
fuel economy during
engine warm-up. Usually,
the coolant heater
should be plugged in a
minimum of four hours
prior to starting your
vehicle.
At temperatures above 32ÉF (0ÉC), use of the coolant
heater is not required.
2-20

Warning Lights, Gages and
Indicators
Warning Lights, Gages, and
Indicators
This part describes the warning lights and gages that
may be on your vehicle. The pictures will help you
locate them.
Warning lights and gages can signal that something is
wrong before it becomes serious enough to cause
an expensive repair or replacement. Paying attention to
your warning lights and gages could also save you
or others from injury.
Warning lights come on when there may be or is a
problem with one of your vehicle's functions. As you will
see in the details on the next few pages, some
warning lights come on brie¯y when you start the
engine just to let you know they're working. If you are
familiar with this section, you should not be alarmed
when this happens.Gages can indicate when there may be or is a problem
with one of your vehicle's functions. Often gages
and warning lights work together to let you know when
there's a problem with your vehicle.
When one of the warning lights comes on and stays on
when you are driving, or when one of the gages
shows there may be a problem, check the section that
tells you what to do about it. Please follow this
manual's advice. Waiting to do repairs can be
costly ± and even dangerous. So please get to know
your warning lights and gages. They're a big help.
Your vehicle also has a driver information system that
works along with the warning lights and gages. See
Driver Information Center (DIC) on page 3-46.
3-27

If, after several seconds, all status indicator lights
remain on, or if there are no lights at all, there may be a
problem with the lights or the passenger sensing
system. See your dealer for service.
{CAUTION:
If the air bag off indicator and the air bag
readiness light ever come on together, it
means that something may be wrong with the
air bag system. If this ever happens, have the
vehicle serviced promptly, because an
adult-size person sitting in the right front
passenger seat may not have the protection of
the air bag. See²Air Bag Readiness Light²in
the Index.
Battery Warning Light
If this light is displayed
when the engine is
running, you may have a
problem with your charging
system.
The battery display will also stay on while the key is in
RUN until the engine is started.
If the light stays on after starting the engine it could
indicate a problem with the generator drive belt, or some
other charging system problem. Have it checked right
away. Driving with this light displayed could drain
your battery.
If you must drive a short distance with this light
displayed, it helps to turn off all your accessories, such
as the radio and the air conditioner.
3-35

Notice:If you drive your vehicle with the
transmission temperature gage above normal
operating range, you can damage the transmission.
This could lead to costly repairs that would not
be covered by your warranty. Do not drive your
vehicle while the transmission temperature gage
reading is above normal. See your dealer for service.
The following situations can cause the transmission to
operate at higher temperatures:
·Towing a trailer
·Hot outside air temperatures
·Hauling a large or heavy load
·Low transmission ¯uid level
·High transmission ¯uid level
·Restricted air ¯ow to the radiator and the auxiliary
transmission oil cooler (if equipped).
A temporary solution to hotter transmission operating
temperatures may be to let the transmission cool down.
If the transmission is operated at higher temperatures
on a frequent basis, see
Scheduled Maintenance
on page 6-4for the proper transmission maintenance
intervals.
Malfunction Indicator Lamp
Check Engine Light
Your vehicle is equipped
with a computer which
monitors operation of the
fuel, ignition and emission
control systems.
This system is called OBD II (On-Board
Diagnostics-Second Generation) and is intended to
assure that emissions are at acceptable levels for the
life of the vehicle, helping to produce a cleaner
environment. The Check Engine light comes on to
indicate that there is a problem and service is required.
Malfunctions often will be indicated by the system
before any problem is apparent. This may prevent more
serious damage to your vehicle. This system is also
designed to assist your service technician in correctly
diagnosing any malfunction.
3-40

Notice:If you keep driving your vehicle with this
light on, after a while, your emission controls
may not work as well, your fuel economy may not
be as good and your engine may not run as
smoothly. This could lead to costly repairs that may
not be covered by your warranty.
Notice:Modi®cations made to the engine,
transmission, exhaust, intake or fuel system of your
vehicle or the replacement of the original tires
with other than those of the same Tire Performance
Criteria (TPC) can affect your vehicle's emission
controls and may cause this light to come on.
Modi®cations to these systems could lead to costly
repairs not covered by your warranty. This may
also result in a failure to pass a required Emission
Inspection/Maintenance test.
This light should come on, as a check to show you it is
working, when the ignition is on and the engine is
not running. If the light does not come on, have it
repaired. This light will also come on during a
malfunction in one of two ways:
·Light FlashingÐ A mis®re condition has been
detected. A mis®re increases vehicle emissions
and may damage the emission control system on
your vehicle. Diagnosis and service may be
required.
·Light On SteadyÐ An emission control system
malfunction has been detected on your vehicle.
Diagnosis and service may be required.
If the Light is Flashing
The following may prevent more serious damage to
your vehicle:
·Reducing vehicle speed.
·Avoiding hard accelerations.
·Avoiding steep uphill grades.
·If you are towing a trailer, reduce the amount of
cargo being hauled as soon as it is possible.
If the light stops ¯ashing and remains on steady, see ªIf
the Light Is On Steadyº following.
If the light continues to ¯ash, when it is safe to do so,
stop the vehicle.Find a safe place to park your vehicle.
Turn the key off, wait at least 10 seconds and restart
the engine. If the light remains on steady, see ªIf
the Light Is On Steadyº following. If the light is still
¯ashing, follow the previous steps, and see your dealer
for service as soon as possible.
3-41

If the Light Is On Steady
You may be able to correct the emission system
malfunction by considering the following:
Did you recently put fuel into your vehicle?
If so, reinstall the fuel cap, making sure to fully install
the cap. See
Filling Your Tank on page 5-6. The
diagnostic system can determine if the fuel cap has
been left off or improperly installed. A loose or missing
fuel cap will allow fuel to evaporate into the atmosphere.
A few driving trips with the cap properly installed
should turn the light off.
Did you just drive through a deep puddle of water?
If so, your electrical system may be wet. The condition
will usually be corrected when the electrical system
dries out. A few driving trips should turn the light off.
Have you recently changed brands of fuel?
If so, be sure to fuel your vehicle with quality fuel. See
Gasoline Octane on page 5-4. Poor fuel quality will
cause your engine not to run as efficiently as designed.
You may notice this as stalling after start-up, stalling
when you put the vehicle into gear, mis®ring, hesitation
on acceleration or stumbling on acceleration. (These
conditions may go away once the engine is warmed up.)
This will be detected by the system and cause the
light to turn on.If you experience one or more of these conditions,
change the fuel brand you use. It will require at least
one full tank of the proper fuel to turn the light off.
If none of the above steps have made the light turn off,
your dealer can check the vehicle. Your dealer has
the proper test equipment and diagnostic tools to ®x any
mechanical or electrical problems that may have
developed.
Emissions Inspection and Maintenance
Programs
Some state/provincial and local governments have or
may begin programs to inspect the emission control
equipment on your vehicle. Failure to pass this
inspection could prevent you from getting a vehicle
registration.
Here are some things you need to know to help your
vehicle pass an inspection:
Your vehicle will not pass this inspection if the Check
Engine light is on or not working properly.
Your vehicle will not pass this inspection if the OBD
(on-board diagnostic) system determines that critical
emission control systems have not been completely
diagnosed by the system. The vehicle would be
considered not ready for inspection.
3-42

This can happen if you have recently replaced your
battery or if your battery has run down. The diagnostic
system is designed to evaluate critical emission
control systems during normal driving. This may take
several days of routine driving. If you have done this and
your vehicle still does not pass the inspection for lack
of OBD system readiness, your GM dealer can prepare
the vehicle for inspection.
Oil Pressure Gage
The oil pressure gage shows the engine oil pressure in
psi (pounds per square inch) when the engine is
running. Canadian vehicles indicate pressure in kPa
(kilopascals).Oil pressure may vary with engine speed, outside
temperature and oil viscosity, but readings above the
low pressure zone indicate the normal operating range.
A reading in the low pressure zone may be caused
by a dangerously low oil level or some other problem
causing low oil pressure. Check your oil as soon
as possible. See
DIC Warnings and Messages on
page 3-57andEngine Oil on page 5-11.
{CAUTION:
Do not keep driving if the oil pressure is low. If
you do, your engine can become so hot that it
catches ®re. You or others could be burned.
Check your oil as soon as possible and have
your vehicle serviced.
Notice:Lack of proper engine oil maintenance may
damage the engine. The repairs would not be
covered by your warranty. Always follow the
maintenance schedule in this manual for changing
engine oil. United States
Canada
3-43