Cruise Descent Control and Deceleration Modes, Detroit™ Engines
On vehicles equipped with a Detroit engine, the functions of the engine brake controls change, depending on which specialty braking mode is being utilized. Two distinct modes can be activated:
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Cruise Descent Control Mode—engine braking attempts to maintain a set speed; accelerator pedal is not automatically applied.
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Deceleration Mode—engine braking activates to reduce vehicle speed (with no lower limit) at a constant rate.
Cruise Descent Control Mode
Note: Before engaging Cruise Descent Control, determine an appropriate speed for the vehicle’s load and grade of the road.
The cruise descent control mode helps control the vehicle and engine speed when descending a grade.
To activate the cruise descent control mode, manually set the engine brakes with the shifter stalk and, while the engine brakes are actively working, set cruise to the desired descent speed. A cruise descent control mode engaged icon will appear on the ICUC screen showing it is active. See Fig..
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Icon Showing Cruise Descent Control Mode Engaged
Fig. 1, Cruise Descent Control Active
The cruise descent control mode will attempt to manage the vehicle’s speed by varying the engine brake level.
The driver should be ready to intervene by applying the service brakes if the grade is too steep and the vehicle is traveling too fast. Applying the service brake to slow the vehicle will not cancel cruise control. Once the service brake is released, the vehicle speed becomes the new cruise descent control set speed. A pop-up will appear on the instrument cluster screen to notify the driver of the new speed. See Fig..
Fig. 2, New Descent Mode Set Speed Pop-Up
When the vehicle’s descent is complete, return the engine brake stalk to the OFF/Auto position. At this point the cruise descent control set speed will become the new cruise speed.
Deceleration Mode
Deceleration mode reduces the vehicle speed at a constant rate.
While in cruise control, activate Deceleration Mode by turning on the engine brake, shown in Fig., lever position 1, 2, or 3. The vehicle will decelerate at a constant rate until the vehicle comes to a stop, unless the accelerator pedal is applied to override the deceleration, or the lever is moved to ‘engine brake off’ (position 0).
Moving the lever to position 0 resumes the previously set cruise control speed.
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Resume cruise control set speed.
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Low
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Medium
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High