7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS 519
SCCS (Speed Control Command Switches)
Figure 495 Function diagram for the SCCS
The function diagram for the SCCS includes the
following:
• Electronic System Co nt ro ller (ESC)
• Electronic Control Module (ECM)
• Steering wheel cruise control switches
Cruise Control
The ECM will control engine speed to maintain a
constant road speed with cruise control. Pressing the
set switch when the vehicle is at the desired speed
withtheCRUISEswitchintheonpositionactivates
the cruise control. Speed is increased or decreased
by pressing ACCEL/CRUISE switches. The cruise
control is deactivated by pressing the off switch,
applying the brake pedal, clutch pedal, or on vehicles
equipped with automatic transmissions, by placing
thetransmissioninneutral.
Power Takeoff (PTO) Control
Engine speed can be controlled by the SCCS switches
if the PTO option has been programmed into the
ECM and the v eh icle is stationary. Variable as
well as preset speeds are available depending on
ECM programming. The PTO function is turned
on by pressing the cruise switch on. Pressing the
SET/CRUISE or RESUME/ACC EL switches will
increase or decrease engine speed depending on
PTO programming.
SCCS Circuit Operation
Cruise control a llows the ECM to control the en gines
power delivery to maintain a constant vehicle speed.
The speed set point is determined by the operator and
the cruise high and low set points are programmed in
the ECM. The minimum engine speed that the cruise
control can be engaged is programmed in the ECM.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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