Rear Heating System
If the vehicle has a crew
cab and has a rear heater,
the thumbwheel for this
feature is located on
the headliner.
To increase and decrease the flow of heated air to the
rear floor vents, turn the thumbwheel to the desired
fan speed. To turn the fan off, turn the thumbwheel all
the way down.
Warning Lights, Gages, and
Indicators
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
the warning lights and gages could prevent injury.
Warning lights come on when there may be or is a
problem with one of the vehicle’s functions. Some
warning lights come on briefly when the engine is started
to indicate they are working.
Gages can indicate when there may be or is a problem
with one of the vehicle’s functions. Often gages and
warning lights work together to indicate a problem with
the vehicle.
When one of the warning lights comes on and stays on
while driving, or when one of the gages shows there
may be a problem, check the section that explains what
to do. Follow this manual’s advice. Waiting to do
repairs can be costly and even dangerous.
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{CAUTION:
If the airbag readiness light ever comes on and
stays on, it means that something may be wrong
with the airbag system. For example, the right
front passenger airbag could inflate even though
the airbag on-off switch is turned off.
To help avoid injury to yourself or others, have the
vehicle serviced right away. SeeAirbag Readiness
Light on page 3-27for more information, including
important safety information.
If the word ON is lit, it means that the right front
passenger frontal airbag is enabled (may inflate). See
Airbag Off Switch on page 1-55for more on this,
including important safety information.
Charging System Light
The charging system light
may be located in the
instrument panel cluster, or
with the auxiliary warning
lights in the center of
the instrument panel.
It should come on briefly when you turn on the ignition,
before the engine is running, as a check to show
that it is working.
If it stays on, or comes on while you are driving, have
your vehicle checked right away. You could have a loose
generator drive belt or some other problem.
Driving while this light is on will drain your battery. If you
must drive a short distance with the light on, turn off
your radio and other accessories. Sustained driving with
a generator failure could result in a lack of back-up
braking if the engine quits or the power steering pump
should fail.
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If the light comes on while driving, pull off the road and
stop carefully. The pedal might be harder to push or
might go the floor. It can take longer to stop. If the light
remains on, have the vehicle towed for service. See
Towing Your Vehicle on page 4-23for more information.
The brake warning light may come on, and the
warning tone may sound, when you are turning and
braking at the same time. This is normal. See “Hydraulic
Brake Systems” underBraking on page 4-4.
Parking Brake Warning Light
Your vehicle has a brake warning light. When the
ignition is on, this light will come on when you set your
parking brake. The light will stay on if your parking
brake does not release fully.
This light should also come on when you turn the
ignition key to START. If it does not come on then, have
it fixed so it will be ready to remind you if the parking
brake is applied or has not released fully.
Air Brake System Warning Light
Vehicles with air brake systems have a brake system
warning light on the instrument panel.
The low air warning light
should come on, as a
check, whenever you start
the engine.
However, it is designed to come on, and stay on, when
brake reservoir pressure has dropped below 60 psi
(410 kPa).
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Trailer Antilock Brake System
Warning Light
If your vehicle is connected
to a trailer with antilock
brakes, this light should
come on briefly, as a
check, when you turn on
the ignition.
When this light comes on and stays on, it means there
is something wrong in the trailer Antilock Brake
System (ABS). Have the system repaired immediately.
If an ABS equipped trailer is not connected, this
light is not functional.
Engine Coolant Temperature Gage
This gage shows
the engine coolant
temperature. If the gage
pointer moves into the
red area, your engine
coolant might have
overheated and your
engine may be too hot.
You should pull off the road, stop your vehicle and turn
off the engine as soon as possible.
SeeEngine Overheating on page 5-48. If you have a
Caterpillar
®diesel engine, also see your Caterpillar®
Operation & Maintenance Manual.
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Low Coolant Warning Light
Your vehicle has a low
coolant warning light.
If this light comes on, the
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 for
10 seconds. SeeEngine Coolant (Caterpillar Diesel
Engines) on page 5-47and have your vehicle serviced
as soon as you can.
This light may also come on if your vehicle has the
automatic engine shutdown system and engine
shutdown has begun. SeeEngine Alarm and Automatic
Shutdown on page 2-18for more information.
Wait to Start Light
If your vehicle has the DURAMAX®6.6L diesel engine,
it will have glow plugs and an air intake heater. If your
vehicle has the Isuzu 6H diesel engine, it will have glow
plugs and an inlet heater. If your vehicle has a Caterpillar
engine, it 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 ON/RUN.
Wait until the indicator light goes off before turning the
ignition key to START.
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Malfunction Indicator Lamp
Check Engine Light
A computer system called OBD II (On-Board
Diagnostics-Second Generation) monitors operation
of the fuel, ignition, and emission control systems.
It makes sure that emissions are at acceptable levels
for the life of the vehicle, helping to produce a cleaner
environment.
If this light comes on while
you are driving, two things
can happen.
First, you will not notice any difference in engine
performance, but the tail pipe emissions might increase.
Second, the engine might not run properly or could
stall without warning. If either of these things happen,
see your dealer/retailer for service.This light should come on when the ignition is on, but
the engine is not running, as a check to show it is
working. If it does not come on at all, have it repaired.
Notice:If the vehicle is continually driven with
this light on, after a while, the emission controls
might not work as well, the vehicle’s fuel economy
might not be as good, and the engine might not
run as smoothly. This could lead to costly repairs
that might not be covered by the vehicle warranty.
Notice:Modifications made to the engine,
transmission, exhaust, intake, or fuel system of the
vehicle or the replacement of the original tires
with other than those of the same Tire Performance
Criteria (TPC) can affect the vehicle’s emission
controls and can cause this light to come on.
Modifications to these systems could lead to costly
repairs not covered by the vehicle warranty. This
could also result in a failure to pass a required
Emission Inspection/Maintenance test. See
Accessories and Modifications on page 5-3.
If the check engine light comes on and stays on, while
the engine is running this indicates that there is an
OBDII problem and service is required.
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An emission system malfunction might be corrected by
doing the following:
•If the vehicle has been driven through a deep
puddle of water, the vehicle’s electrical system
might be wet. The condition is usually corrected
when the electrical system dries out. A few driving
trips should turn the light off.
•Make sure to fuel the vehicle with quality fuel. Poor
fuel quality causes the engine not to run as efficiently
as designed and may cause: stalling after start-up,
stalling when the vehicle is changed into gear,
misfiring, hesitation on acceleration, or stumbling on
acceleration. These conditions might go away once
the engine is warmed up.
If one or more of these conditions occurs, change the
fuel brand used. It will require at least one full tank of
the proper fuel to turn the light off.
SeeDiesel Engine Fuel on page 5-8.
If none of the above have made the light turn off, your
dealer/retailer can check the vehicle. The dealer/retailer
has the proper test equipment and diagnostic tools to
fix any mechanical or electrical problems that might have
developed.
Emissions Inspection and Maintenance
Programs
Some state/provincial and local governments have or
might begin programs to inspect the emission control
equipment on the vehicle. Failure to pass this inspection
could prevent getting a vehicle registration.
Here are some things to know to help the vehicle pass
an inspection:
•The vehicle will not pass this inspection if the check
engine light is on with the engine running, or if the
key is in the ON/RUN and the light is not on.
•The vehicle will not pass this inspection if the OBD II
(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. This can happen
if the battery has recently been replaced or if the
battery has run down. The diagnostic system is
designed to evaluate critical emission control
systems during normal driving. This can take several
days of routine driving. If this has been done and the
vehicle still does not pass the inspection for lack of
OBD II system readiness, your dealer/retailer can
prepare the vehicle for inspection.
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Low Oil Level Light
Your vehicle may have a
low oil level light.
This light should come on as a check, when you start
your engine. If the light fails to come on, have it repaired
as soon as possible so you will be aware when the oil
level is low.
Vehicles that have Caterpillar
®diesel engines may not
have a low oil level light. In this case, the light will
neither come on as a check when you start your engine,
nor will it come on to indicate a low oil level.
If this light comes on and stays on, it means your
engine is low on oil. You need to check the oil level
right away. SeeEngine Oil (DURAMAX Diesel Engine)
on page 5-24orEngine Oil (Caterpillar Diesel Engine)
on page 5-27orEngine Oil (Isuzu Diesel Engine)
on page 5-28orEngine Oil (Gasoline Engine) on
page 5-32for further information.Notice:Lack of proper engine oil maintenance
can damage the engine. The repairs would not be
covered by the vehicle warranty. Always follow the
maintenance schedule in this manual for changing
engine oil.
Change Engine Oil Light
The change engine oil light
should come on briefly as
a bulb check when you
start the engine. If the light
does not come on, have
it serviced.
If the change engine oil light comes on and stays on
after you start the engine, have the oil changed.
For additional information on when to change engine oil
for gasoline engines or DURAMAX
®diesel engines, see
Engine Oil (DURAMAX Diesel Engine) on page 5-24or
Engine Oil (Caterpillar Diesel Engine) on page 5-27or
Engine Oil (Isuzu Diesel Engine) on page 5-28orEngine
Oil (Gasoline Engine) on page 5-32andScheduled
Maintenance on page 6-5. To reset the change engine oil
light, seeEngine Oil Life System (Gasoline Engine) on
page 5-35orEngine Oil Life System (DURAMAX/Isuzu
Diesel Engines) on page 5-36orEngine Oil Life System
(Caterpillar Diesel Engine) on page 5-38.
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