Exhaust Restrictor
(Engine Warm-Up)
Exhaust Restrictor
If your vehicle has a Isuzu 6H or Caterpillar®
Diesel Engine, it may have a feature called
an Exhaust Restrictor (NPE), which uses an air
actuated valve in the exhaust system to restrict
exhaust gas flow which enhances the engine and
heater warm-up.
Automatic Quick Warm-Up
If your vehicle has a DURAMAX®6600 engine, it
has a feature called an Automatic Quick
Warm-Up, which uses the turbocharger to restrict
the exhaust gas flow which enhances the
engine and heater warm-up.
In both systems, exhaust restrictor or automatic
quick warm-up, the cold temperature high
idle feature elevates the engines idle speed, up to
1500 rpm, and restricts the exhaust gas flow,
when outside temperatures are below 32°F (0°C),
and the engine coolant temperature is below
certain levels. This feature enhances heater
performance by raising the engine coolant
temperature faster.For all engines this feature is already turned on.
The automatic quick warm-up on the DURAMAX
®
engine can be turned off and on by doing the
following procedure:
1. Turn the ignition to RUN, with the vehicle off.
2. Press the accelerator pedal to the floor
and hold it while quickly pressing and
fully releasing the brake pedal three times in
less than eight seconds.
3. Release the accelerator pedal and start the
engine. The green exhaust brake/restrictor
light below the radio controls will be lit
for 10 seconds.
If this feature is turned off, by doing the
procedure described previously, and then the
engine is started, the exhaust brake/restrictor
light will flash for 10 seconds and then it
will turn off.
When the engine is started, it will slowly increase to
the high idle speed after a delay of a few seconds;
up to about two minutes. For this method to work
properly there must be no throttle or brake pedal
faults, and the throttle pedal must not fall below
75 percent of wide open throttle while pressing the
brake pedal.
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The engine idle speed will return to normal once
the following conditions are met:
•Once engine coolant temperature reaches
about 150°F (65°C).
•The intake temperature reaches a
certain level.
The high idle speed will be temporarily interrupted
and the engine speed will return to normal if
any of the following conditions occur:
•The brake pedal is applied.
•The accelerator pedal is pressed.
•The automatic transmission is shifted out of
PARK (P) or NEUTRAL (N).
•The clutch pedal on the manual transmission
is pressed.
•Vehicle speed is detected.
Once these conditions no longer exist, the engine
idle speed will slowly increase to high idle after
the normal delay, if the conditions for engine
coolant temperature and air intake temperature
are still met.
Engine Checks Before Operating
When you have started your engine, let it run for
20 to 30 seconds before you put a load on the
engine. But do not leave the vehicle while
the engine is running.
Avoid unnecessary idling of diesel engine
equipped vehicles.
If the engine idles too long, the temperature of the
engine coolant will fall below the normal operating
range. Low engine operating temperature
causes several conditions which affect engine
operation and reduce engine life.
The engine should be permitted to go through a
warm-up period. Operate the vehicle at a minimum
of 600 rpm during the warm-up period. During
this period and during operation, the following
observations should be made.
During this warm-up period, check your 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 175for more information.
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•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 173for 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 169for 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 183for
more information.
•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 thegenerator is not charging; it does not reflect
the condition of the battery.) SeeCharging
System Light on page 167for 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 168
for 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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Diesel Engine Exhaust Brake
If your vehicle has a Isuzu 6H or Caterpillar®
Diesel Engine, it may have an exhaust brake,
which is located in the exhaust system.
If your vehicle has a 6.6L DURAMAX
®6600
Diesel Engine, it may have an exhaust brake,
which is controlled through the turbocharger.
The exhaust brake for both engines operates
the same.
The exhaust brake
switch is located in the
instrument panel
switchbank.
Push the bottom of the switch to turn the exhaust
brake on. When you push the top of the switch,
the exhaust brake will turn off.
There is an indicator light on the instrument panel
similar to the symbol on the switch, that will come
on when the exhaust brake is active. SeeExhaust
Brake Indicator Light on page 178for more
information.When using the exhaust brake, the proper gear
range selection is important. The exhaust brake will
be most effective if the gear range selected is the
lowest possible range that does not allow the
engine rpm to go more than 200 rpm above rated
(full load) rpm. If you have a Caterpillar®Diesel
Engine, do not exceed 2900 rpm. If you have a
Isuzu 6H Diesel engine, do not exceed 2550 rpm.
If you have a DURAMAX
®6600 Diesel Engine, do
not exceed 3600 rpm.
If your vehicle has an Allison
®
1000/2200/2300/2500 series automatic
transmission and press this button, the
transmission will downshift to a factory default
setting of third gear. To change the default setting,
or for more information on factory default
settings, contact your dealer for assistance.
The accelerator and clutch pedals must be
released in order for the exhaust brake to engage.
The exhaust brake will automatically shut off
when the anti-lock brake system is active.
If your vehicle has a Caterpillar
®Diesel Engine or
a DURAMAX®6600 Diesel Engine, the exhaust
brake will become active in cruise control
when you exceed the set speed by 3 to 5 mph.
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Air Shift Control (Automatic
Transmission)
The rear axle shift
control switch for an
automatic transmission
is located in the
instrument panel
switchbank.
To use the rear axle shift control, press the bottom
of the switch to get to the high range. The
switch indicator light will come on when the vehicle
is in the high range. Press the top of the switch
to return to the low range.The two-speed axle should be in low range when
you park the vehicle. You will need to engage
the transmission and move the vehicle a little to
assure the axle is in range. Then shift into
PARK (P), apply the parking brake, and shut off
the engine.
To shift up from low to high range while driving,
press the bottom of the rear axle shift control
switch as you are releasing the accelerator pedal.
After the shift has occurred, apply the accelerator
as desired.
To shift from high to low range while driving, press
the top of the rear axle shift control switch as
you release the accelerator pedal. Press the
accelerator pedal slowly until the down shift has
occurred, then apply the accelerator as desired.
For better performance during off-road or under a
heavy load, shift the axle into low range and
then operate the transmission normally.
For better performance on the highway, shift the
axle to high range and operate the transmission
normally.
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Overdrive Defeat
If your vehicle has this feature, you can select not
to shift up to fifth gear. This is useful when
towing or under a heavy load.
The overdrive defeat
switch is located in
the instrument panel
to the right of the
steering column.
Press the switch to limit the transmission to
fourth gear. This will allow for fewer downshifts
while pulling a trailer or under a heavy load.
The indicator light in the switch will come on
whenever overdrive defeat is active.
Manual Transmission Operation
Using the Clutch
When you are starting to move the vehicle, it is
important to begin with the engine speed at idle.
Then start to engage the clutch and listen for an
engine speed drop of about 100 rpm. At this point,
the clutch is engaging, so you should increase the
engine speed and fully engage the clutch. It is
important not to increase the engine speed sooner
or before the clutch begins its engagement. If you
do, you can cause damage to your vehicle.
Double-Clutching
You must use the double-clutching method when
you shift an unsynchronized gear set. Disengage
the clutch, shift to NEUTRAL and engage the
clutch. When upshifting, slow the engine until the
engine rpm and road speed match. When
downshifting, accelerate the engine until the
engine rpm and road speed match. Then quickly
disengage the clutch and move the shift lever
to the next gear position and engage the clutch.
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Clutch Brake (Vehicles with
Non-Synchronized Transmission)
A clutch brake is used to stop transmission input
shaft rotation so that FIRST (1) or REVERSE (R)
gear selection can be initiated when the vehicle is
at a standstill and the engine is idling.
Press the clutch pedal all the way down to the
floorboard to apply the clutch brake.
When using the clutch brake, disengage the clutch
pedal and shift the transmission into either the
initial starting gear or REVERSE (R). If the
tooth-butting occurs between the clutching teeth,
re-engage the clutch while applying light pressure
to the shift lever. This will provide for a smooth
shift into either FIRST (1) or REVERSE (R) gear.
Notice:Using the clutch brake for shifting
into any gear other than FIRST (1) or
REVERSE (R) may cause premature wear of
the clutch brake and make gear shift effort
more difficult. Do not use the clutch brake for
shifting after engaging FIRST (1) or
REVERSE (R).
Power Take-Off (PTO)
If your vehicle is
equipped for the
addition of a PTO, this
factory installed
switch will be located in
the instrument panel.
When the PTO switch is in the ON position,
engine speed is limited to maximum PTO speed if
PTO is activated during driving; therefore
limiting overall vehicle speed.
Before using a PTO, refer to the manufacturer’s or
installer’s instructions.
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If your vehicle has
four-wheel drive, the
transfer case knob
is located to the right of
the steering wheel
on the instrument panel.
Use this knob to shift
into and out of
four-wheel drive.
An indicator light shows you which position the
transfer case is in. The indicator lights come
on briefly when you turn on the ignition and
one stays on. If the lights do not come on, you
should take your vehicle to your dealer for service.
An indicator light flashes while shifting the
transfer case. It will remain on when the shift is
complete. If for some reason the transfer
case cannot make a requested shift, it returns to
the last chosen setting.Recommended Transfer Case Settings
Driving ConditionsTransfer Case Settings
2m4m4nN
Normal YES
Severe YES
Extreme YES
Vehicle in Tow* YES
*SeeTowing Your Vehicle on page 241for further
information.
2m(Two-Wheel High):This setting is for driving
in most street and highway situations. The
transfer case does not drive the front axle in
two-wheel drive. The front-axle spins if the front
wheel hubs are locked. Be sure to unlock the hubs
to achieve the best fuel economy.
4
m(Four-Wheel High):Use Four-Wheel High
when you need extra traction, such as on snowy or
icy roads or in most off-road situations. Be sure
the front wheel hubs are locked when you want to
drive in Four-Wheel High.
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