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STARTING AND OPERATING 137
If the engine is allowed to idle or the truck is driven
on low engine speed drive cycles for more than
two hours, the system will automatically enter an
emissions operating mode that will increase the
engine idle speed to 900 RPM. While in this mode,
which is designed to help maintain the diesel
particulate filter, the engine idle speed will return
to normal when the brake pedal is applied. A small
change in engine tone or a slight change in engine
performance while accelerating may also be
noticeable at speeds below 20 mph (32 km/h).
This operating mode may last for up to an hour of
idle time, or around 20 minutes of driving time.
Your truck may have been ordered with an optional
voltage monitoring Idle-Up feature. If a load is placed on
the electrical system while the truck is in park, this
feature will attempt to maintain normal system voltage
by automatically increasing engine idle speed. You may
notice several consecutive increases in idle speed,
up to a maximum of 1,450 RPM, as the system will
attempt to utilize the smallest increase in idle speed
necessary to maintain normal system voltage. The idle
speed will return to normal when either the electrical
load is removed, or when the brake pedal is applied.
NOTE:
For instrument cluster display messages related to
the vehicle's exhaust system Ú page 104.
Idle-Up Feature
The driver-controlled high idle speed feature will
help increase cylinder temperatures and provide
additional cab heat, however, excessive idling may
still cause the exhaust aftertreatment system to
not properly regenerate. Extended periods of idle
time should be avoided.
The Idle-Up feature uses the Cruise Control buttons
to increase engine idle speed and quickly warm the
vehicle's interior.
1. With the transmission in PARK, the parking
brake applied, and the engine running, push
the On/Off button to the ON position, then
push the SET (-) button.
2. The engine RPM will go up to 1,100 RPM. To
increase the RPM, push and hold the RES (+)
button and the idle speed will increase to approxi-
mately 1,500 RPM. To decrease the RPM, push
and hold the SET (-) button and the idle speed will
decrease to approximately 1,100 RPM.
3. To cancel the Idle–Up feature, either push the
CANCEL button, push the On/Off button, or
press the brake pedal.
NOISE
Diesel engines can create noises that may seem
concerning. The nature of a diesel engine is
compression ignition where compressed air and fuel
are mixed and ignited. Weather, barometric pressure,
altitude, and temperature will affect how fuel is ignited
in the engine. Engines will sound different from day to
day or previous model years. Clicking, ticking, or light
knocking is normal and will change from day to day, as
the engine breaks in, and can vary with changes in
ambient temperature. Clicking sound from under the
hood shortly after vehicle shutdown is normal as
actuators such as the EGR valve are cycled. Fuel pump
noise may increase during low speed/light load
conditions when ambient temperature is above 100°F
(38°C), and when fuel tank level is below 10% which is
a normal condition of the fuel system and controls
strategy. Diesel equipped vehicles also have an
exhaust after-treatment system to reduce emissions
utilizing a Diesel Particulate Filter (DPF) and a Selective
Reduction Catalyst (SCR). The SCR reduces Nitrogen
Oxides (NOx) using the Diesel Exhaust Fluid (DEF)
system. DEF is injected directly into the SCR through a
dosing module. This process will create a clicking
sound and at times, will make noise even with the
vehicle shut off. This is normal as the DEF dosing
module is purging DEF. If at any time the Check Engine
Light is on, please visit an authorized dealer.
4
22_DJD2_OM_EN_USC_t.book Page 137
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