1999 CHEVROLET TAHOE engine

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2-76 Engine Coolant Temperature Gage
This gage shows the engine
coolant temperature.
It also provides an indicator of how hard your vehicle is
working. During a majority of the operation, the gage
will read 210
F (100
C) or less. If you are pulling a
load or going up hills, it is normal for the temperature to
fluctuate and approach the 260
F (160
C) mark. If the
gage reaches the 260
F (160
C) mark, it indicates that
the cooling system is working beyond its capacity.
The ªProblems on the Road,º section of this manual
shows what to do. See ªEngine Overheatingº in
the Index.
Malfunction Indicator Lamp (Service
Engine Soon Light) (Gasoline Engine)
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 SERVICE ENGINE SOON 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.

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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:
Modifications made to the engine, transmission,
exhaust 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 the SERVICE ENGINE SOON
light to come on. Modifications 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 doesn't come on, have it repaired.
This light will also come on during a malfunction in one
of two ways:

Light Flashing
-- A misfire condition has been
detected. A misfire increases vehicle emissions and
may damage the emission control system on your
vehicle. Dealer or qualified service center diagnosis
and service may be required.

Light On Steady
-- An emission control system
malfunction has been detected on your vehicle.
Dealer or qualified service center 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.

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If the light stops flashing and remains on steady, see ªIf
the Light Is On Steadyº following.
If the light continues to flash, 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 flashing,
follow the previous steps, and drive the vehicle to your
dealer or qualified service center for service.
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 ªFilling Your Tankº in the Index. 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
ªFuelº in the Index). 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, misfiring, 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,
have your dealer or qualified service center check the
vehicle. Your dealer has the proper test equipment and
diagnostic tools to fix any mechanical or electrical
problems that may have developed.

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2-79 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 other problem causing low
oil pressure. Check your oil as soon as possible.CAUTION:
Don't keep driving if the oil pressure is low. If
you do, your engine can become so hot that it
catches fire. You or others could be burned.
Check your oil as soon as possible and have your
vehicle serviced.
NOTICE:
Damage to your engine from neglected oil
problems can be costly and is not covered by
your warranty.

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2-80 Security Light
This light will come on
briefly when you turn the
key to START.
The light will stay on until the engine starts. If the light
flashes, the Passlock

System has entered a tamper
mode. If the vehicle fails to start, see ªPasslockº in
the Index.
If the light comes on continuously while driving and
stays on, there may be a problem with the Passlock
System. Your vehicle will not be protected by Passlock,
and you should see your GM dealer.
Service Four-Wheel Drive Warning Light
(If Equipped)
If your vehicle is equipped with the automatic
four
-wheel-drive transfer case, it has a computer which
controls the four
-wheel-drive system.
This light should come on
briefly when you turn on the
ignition, as a check to show
you it is working.
The SERVICE 4WD light comes on to indicate that
there may be a problem with the automatic
four
-wheel-drive system and service is required.
Malfunctions can be indicated by the system before
any problem is apparent, which may prevent serious
damage to the vehicle. This system is also designed
to assist your service technician in correctly diagnosing
a malfunction.

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2-81 Daytime Running Lamps (DRL)
Indicator Light
This light will go on
whenever the DRL are on.
When it begins to get dark, the DRL indicator light is a
reminder to turn on your headlamps.
Check Gages Light
This light will come on
briefly when you are
starting the engine.
If the light comes on and stays on while you are driving,
it could indicate a problem with your vehicle. It could bea problem with your oil pressure, coolant temperature,
or some other problem. Check your various gages to see
if they are in the warning zones. If they are, have your
vehicle serviced right away.
Headlamp High-Beam Indicator Light
The high-beam indicator is
on whenever you use your
high
-beam headlamps. For
more details about high
beams, see ªHeadlamp
High/Low
-Beam Changerº
earlier in this section.
Turn Signal and Lane Change
Indicator Lights
The signal indicator will
come on whenever you
signal a turn or lane change.
See ªTurn Signal and Lane
Change Indicatorº earlier in
this section.

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2-82 Fuel Gage
When the ignition is on, the
fuel gage tells you about
how much fuel you have
left in your tank.
The gage will first indicate E (empty) before you are out
of fuel, and you should get more fuel as soon
as possible.
Listed are four situations you may experience with your
fuel gage:

At the gas station, the fuel pump shuts off before the
gage reads F (full).
It takes a little more or less fuel to fill up than the
fuel gage indicated. For example, the gage may have
indicated the tank was half full, but it actually took a
little more or less than half the tank's capacity to fill
the tank.

The gage moves a little when you turn a corner or
speed up.

The gage doesn't go back to E (empty) when you
turn off the ignition.
None of these indicate a problem with the fuel gage.
For information on how to fill your fuel tank, see
ªFuel
-- Filling Your Tankº in the Index.
For your fuel tank capacity, see ªFuel
-- Tank Capacityº
in the Index.
For the diesel engine fuel gage, see your Diesel
Engine Supplement.

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3-7 Air Conditioning
On hot days, open the windows long enough to let hot
air inside escape. This reduces the time it takes for your
vehicle to cool down. Then keep your windows closed
for the air conditioner to work its best.
The recirculation button, between the fan and
temperature knobs, allows the air inside your vehicle to
be recirculated. This setting helps to maximize your air
conditioner's performance and your vehicle's fuel
economy. This setting also cools the air the fastest and
can be used to keep unwanted odors and/or dust from
entering the vehicle. When using the air conditioner,
turn off recirculation after the vehicle reaches a
comfortable interior temperature. When the right knob
on the control panel is between HEATER and
DEFROST, the recirculation feature will not function.
The A/C button, between the temperature and mode
knobs, allows the air coming into your vehicle to be
cooled. This setting is useful for normal cooling on hot
days. When you use A/C with the recirculation button
pushed in, turn off recirculation as soon as the vehicle
reaches a comfortable interior temperature.With the A/C on, move the temperature knob to MAX
for maximum cooling. This setting also puts the system
in the recirculation mode and helps to maximize your air
conditioner's performance and your vehicle's fuel
economy. This setting also cools the air the fastest. After
the vehicle's interior reaches a comfortable temperature,
move the temperature knob clockwise to place the air
conditioning system in the normal mode.
Heating
The heater works best if you keep your windows closed
while using it. On cold days, use the HEATER or
VENT/HEAT setting with the temperature knob in the
red area.
If you use the engine coolant heater before starting your
engine in cold weather, 20
F (
-8
C) or lower, your
heating system will produce warmer air faster, to heat
the passenger compartment in cold weather.
The use of an engine coolant heater also reduces the
time it takes for the engine to reach normal operating
temperature, and shortens the time it takes the heater to
reach full output. For more information, see ªEngine
Coolant Heaterº in the Index.