
If the 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 the engine will not start,
do this:
Turn the ignition key to ON/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 the engine again. And, see your dealer/retailer
as soon as you can for a starting system check.
If the light comes on and then goes off and you know
the batteries are charged, but the engine still will
not start, the vehicle needs service.
If the light does not come on when the engine is cold,
the vehicle needs service.If the batteries do not have enough charge to start the
engine, seeBattery on page 5-61.
Be sure you have the right oil for the engine, and that
you have changed the oil at the proper times. If you use
the wrong oil, the 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, the
vehicle needs service.
{CAUTION:
Do not use gasoline or starting aids, such as
ether, in the air intake. They could damage the
engine. There could also be a fire, which could
cause serious personal injury.
2-17

During this warm-up period, check the warning lights
and gages:
•If oil pressure does not begin to rise within
15 seconds of starting, stop the engine and find the
cause. SeeOil Pressure Gage on page 3-38for
more information.
•If the engine coolant temperature gage needle goes
into the hot area on the gage, stop the engine and
find the cause of the overheating. SeeEngine
Coolant Temperature Gage on page 3-34for more
information.
•If you have air brakes, the dual-needle air pressure
gage should read at least 115 psi (790 kPa) for both
service systems before you try to move the vehicle.
When air pressure is below 60 psi (420 kPa), the
LOW AIR light will come on and you will hear a
tone alarm. SeeBrake System Warning Light on
page 3-31for more information. If the pressure does
not build up or drops during warm-up, stop the
engine and find the cause before you try to move the
vehicle. Recommended air pressure before driving is
120 psi (830 kPa). SeeAir Pressure Gage on
page 3-47for more information.
•The charging system light should come on when the
ignition key is turned to ON/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 3-29for more information.
•The voltmeter charge indicator gage tells you the
condition of the 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 3-30for more information.
Notice:Do not allow the engine to operate at low
idle for more than five 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.
2-24

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 1-48.
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 ON/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 the
vehicle is started or comes on while driving, it
means the airbag system might not be working
properly. The airbags in the vehicle might not
inflate in a crash, or they could even inflate
without a crash. To help avoid injury, have the
vehicle serviced right away.
3-27

Range Inhibit Warning Indicator
If your vehicle has an Allison 1000/2200/2300/
2500 series automatic transmission, a lighted bar
under the current gear selected will flash.
If your vehicle has an Allison 3000/3500 series automatic
transmission, the current gear selected on the pushbutton
display will flash.
The flashing bar or gear selection indicates that
transmission range shifts may not occur.
For detailed information on shift inhibit limitations, see
the Allison Automatic Transmission Operator’s Manual in
your vehicle for further information.
Brake System Warning Light
Your vehicle has either hydraulic or air brakes. Each
system has different warning lights.
Hydraulic Brake System Warning Lights
Vehicles with hydraulic brake systems have two brake
system warning lights on the instrument panel.
If the brake warning light
comes on, it means that the
fluid level in the master
cylinder reservoir is low or
there is another problem
with your hydraulic brakes.
When it comes on, you will also hear a warning tone.
This light should come on briefly when you turn the
ignition key to ON/RUN. If it does not come on, then have
it fixed so it will be ready to warn you if there is a problem.
3-31

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).
3-32

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.
3-35

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.
3-37

Aftermarket Engine Performance
Enhancement Products and
Modifications
Some aftermarket engine performance products and
modifications promise a way to increase the horsepower
and torque levels of the vehicle’s powertrain. You should
be aware that these products could have harmful effects
on the performance and life of the engine, exhaust
emission system, transmission, and drivetrain. The
engines, transmissions, and drivetrains have been
designed and built to offer industry leading durability and
performance in the most demanding applications. Engine
power enhancement products may enable the engine to
operate at horsepower and torque levels that could
damage, create failure, or reduce the life of the engine,
engine emission system, transmission, and drivetrain.
Damage, failure, or reduced life of the engine,
transmission, emission system, drivetrain, or other
vehicle components caused by aftermarket engine
performance enhancement products or modifications
might not be covered under the vehicle warranty.
California Proposition 65 Warning
Most motor vehicles, including this one, contain and/or
emit chemicals known to the State of California to cause
cancer and birth defects or other reproductive harm.
Engine exhaust, many parts and systems (including
some inside the vehicle), many fluids, and some
component wear by-products contain and/or emit
these chemicals.
California Perchlorate Materials
Requirements
Certain types of automotive applications, such as airbag
initiators, seat belt pretensioners, and lithium batteries
contained in remote keyless transmitters, may contain
perchlorate materials. Special handling may be
necessary. For additional information, see
www.dtsc.ca.gov/hazardouswaste/perchlorate.
5-4