GMC 2003 GMT560 T-Series, Owner'S Manual

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Manual High Idle System
If your vehicle has this
feature, the manual high
idle switch is located in the
instrument panel
switchbank.
This system can be used to increase your engine idle
speed whenever the following conditions are met:
•
The brake pedal is not pressed.
•
The vehicle is at a complete stop.
•
The manual transmission (if equipped) clutch pedal
is not pressed or, the automatic transmission (if
equipped) is in NEUTRAL (N) or PARK (P).
The manual high idle feature is activated by pressing
the switch on the instrument panel. When the switch is
pressed again, or any of the previous conditions are
not met, manual high idle will be deactivated.
Exhaust Restrictor
If your vehicle is equipped with this feature, there is an
exhaust restrictor valve located in the exhaust stream.
The valve closes to provide back pressure to the engine
for the purpose of warming the engine quickly.
The exhaust restrictor operates:
•
while the engine is running.
•
while the vehicle is not moving.
•
while the accelerator, brake and clutch pedals are
not pressed.
•
while idling or driving in cold temperatures.
•
when the shift lever is in NEUTRAL (N) or
PARK (P).
On vehicles equipped with a diesel engine exhaust
brake, the exhaust brake switch must be on. The
indicator in the exhaust brake switch will be lit when the
exhaust restrictor is active. The exhaust brake
indicator light in the center of the instrument panel will
also be lit whenever the exhaust restrictor is active.
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