GMC 2003 C4C042 Owner's Manual page 97

Manual High Idle System (If Equipped)
This system can be used to increase your engine idle
speed whenever the following conditions are met:
D
The brake pedal is not pressed.
D
The vehicle speed is below approximately 5 mph
(8 km/h) for vehicles with diesel engines. The
vehicle must not be moving and the accelerator must
not be pressed for vehicles with gasoline engines.
D
The manual transmission (if equipped) clutch
pedal is not pressed or, the automatic transmission
(if equipped) is in NEUTRAL (N) or PARK (P).
2-22
If your vehicle has this
feature, the manual high
idle switch is located in the
instrument panel
switchbank.
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.
The manual high idle has been preset at the factory.
Your dealer may change the setting to fit your needs.
For vehicles with Caterpillar diesel engines, manual
high idle can be used to set any desired high idle speed.
To set a new temporary engine idle speed:
1. Make sure all of the previously described conditions
are met.
2. Press the accelerator pedal to the desired
engine speed.
3. Momentarily press the manual high idle switch.
The temporary high idle speed will be set. This new
high idle rpm level will be remembered by the system
until either the ignition is turned to OFF or a new high
idle speed is set.