General Description, Cruise Descent Control and Deceleration Modes
Note: As a feature of cruise control, descent control mode will work with all transmission options; however, cruise control can only request a specific gear if the vehicle is equipped with a DT12. Descent control mode with transmissions other than D12 is therefore limited.
On vehicles equipped with a Detroit DT12 automated transmission, 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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Descent control mode: engine braking attempts to maintain a set speed; the accelerator pedal is not automatically applied. Setting the cruise control speed with the engine brake on will activate cruise descent control mode. Moving the transmission shift lever to the top position will resume the set cruise speed.
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Deceleration mode: engine braking activates to reduce vehicle speed (with no lower limit) at a constant rate. Moving the transmission shift lever down to engage the engine brake after the cruise control has been set will activate deceleration mode.