264
Driver assist systems
Disengaging conditions
Downhill speed control is disengaged when:
– The steering wheel switch 'OFF' is pressed.
–
– The vehicle speed falls below 25 km/h (15 mph).
– The accelerator pedal is operated for a certain time and the speed exceeds the
downhill speed control speed, without interruption of the drive line.
If the speed of the vehicle increases, the exhaust brake is first actuated. If the speed
still increases, the MX Engine Brake or the retarder are also actuated to maintain the
desired downhill speed control speed. If the speed decreases, the MX Engine Brake or
retarder are deactivated first to maintain the desired downhill speed control speed.
However, the function remains active, so when the vehicle speed exceeds the set
speed, the MX Engine Brake or retarder is activated again. If the speed decreases
further, the exhaust brake is deactivated as well.
When the MX Engine Brake or retarder is active, the green warning
indicator on the instrument panel is visible.
NOTE: If configured, at the same time the automated gearbox selects the
right gear for the optimum speed range for engine brake operation.
CAUTION: The use of the retarder increases the temperature of the
cooling system. To avoid overheating the cooling system, it is
possible that the braking performance of the retarder might be
reduced or even shut off. This can lead to dangerous situations.
– If the retarder braking performance is reduced or shut off due to
overheating, use the brake pedal to reduce vehicle speed.
– Keep the engine speed high to decrease the temperature of the
cooling system.
NOTE:
– With downhill speed control the maximum braking torque can be
reached.
– When ABS is in use, the retarder switches off for as long as ABS is in
operation.
DW63246305.book Page 264 Friday, March 22, 2019 4:54 PM
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