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STARTING AND OPERATING 225
Your vehicle is equipped with an engine warm
up protection feature that may limit engine
performance after cold starting at low ambient
temperatures. The length of time engine speed
is limited is dependent upon engine coolant
temperature. Engine speed may be briefly
limited to 1000 RPM after starting with coolant
temperature below freezing conditions, and
may be limited to 1000 RPM for up to
approximately 2 minutes under more severe
cold conditions.
NOTE:
If ambient temperatures are low and the
coolant temperature is below 180°F (82°C),
the engine idle speed will slowly increase to
1,000 RPM after two minutes of idle, if the
following conditions are met:
Foot is off brake pedal and throttle pedal.
Automatic transmission is in PARK.
Vehicle speed is 0 mph (0 km/h).
Applying the throttle will cancel fast idle.
Operating the exhaust brake at idle will
greatly improve warm up rate and will help
keep the engine close to operating tempera-
ture during extended idle.
ENGINE IDLING
Avoid prolonged idling, long periods of idling
may be harmful to your engine because
combustion chamber temperatures can drop so
low that the fuel may not burn completely.
Incomplete combustion allows carbon and
varnish to form on piston rings, engine valves,
and injector nozzles. Also, the unburned fuel
can enter the crankcase, diluting the oil and
causing rapid wear to the engine.
If the engine is allowed to idle or the truck is
driven on low engine speed drive cycles for
more than 2 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, refer to
“Instrument Cluster Display” in “Getting To
Know Your Instrument Panel” for further infor-
mation.
5
20_DJD2_OM_EN_USC_t.book Page 225
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