Detailed description, cruise control
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Detailed description, cruise control
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Cruise control is operated with the switch on the direction indicator stalk switch. The switch is powered from +54 and has three outputs to the control module (see adjacent table).
When the switch is put in position "ON", the control module will send bus information "CRUISE lamp ON". The main instrument unit will then turn on the lamp.
When the "SET" button is subsequently pressed, the control module will store the current speed in its memory on condition that other conditions for cruise control have been fulfilled.
The ECM then reads the nominal rolling resistance stored in a table for different vehicle speeds on level ground. The result is an engine torque request in order to keep vehicle speed constant.
Vehicle speed lower than requested
If the vehicle speed is lower than the request from the cruise control function, the ECM will increase the requested engine torque until the vehicle speed is the same as the requested speed. The maximum engine torque that the cruise control can request is limited to optimise passenger comfort. Similarly the incremental increase of engine torque is limited to avoid too sudden acceleration.
Vehicle speed is higher than requested
If the vehicle speed is higher than the request from the cruise control function, the ECM will decrease the requested engine torque until the vehicle speed is the same as the requested speed. The torque reduction is filtered to optimise passenger comfort. Note than on steep descents, vehicle speed may exceed the cruise control function's request.
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Note
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For safety reasons (brake system function) the driver is required to apply the brakes at least once before the system can be activated. If the driver tries to activate the cruise control without having tested the brakes, the SID will display: Tap brakes lightly before using cruise control.
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Activating cruise control
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Conditions for activation
The following conditions must be fulfilled before cruise control can be engaged:
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1.
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Brake light switch in rest state.
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2.
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Clutch and brake pedal in rest position.
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3.
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Vehicle speed (front wheels) exceeds 25 km/h.
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4.
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Vehicle speed (rear wheels) exceeds 25 km/h.
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5.
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Decelleration limited.
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6.
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No TC active (bus from ESP).
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8.
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Brake pedal activated prior to cruise control activation.
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10.
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Inputs A, B and C = 0 prior to switch being moved to ON/OFF.
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11.
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No DTCs regarding cruise control generated.
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Switch function
From switch pin
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To control module pin
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SWITCH POSITION
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Zero position
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ON/OFF
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SET/+
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RESUME/-
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CANCEL
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8
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78(B)
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0
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1
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0
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0
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0
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10
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56(B)
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0
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1
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1
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0
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1
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9
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77(B)
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0
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1
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0
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1
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1
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Zero position
The switch is spring-loaded to zero position. None of the switch connections A, B or C are energized.
ON/OFF
When the switch is moved to the far left, connections A, B and C are energized. The ON/OFF switch has two functions, alternately ON and OFF.
CANCEL
Between zero position and ON/OFF, switch connections B and C are energized. This position has the same function as when the brake pedal or clutch pedal is depressed, i.e. cruise control is disengaged but the set speed is retained in memory.
RESUME/-
When the switch is moved to the right from zero position, connection C is energized. This position has three functions:
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1.
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Engages cruise control and stores the current speed in memory unless a speed is already stored there.
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2.
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Engages cruise control if the speed is stored in memory but cruise control was cancelled with CANCEL, the brake or the clutch.
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3.
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If the position is selected while cruise control is active, the speed will decrease. When the switch returns to zero position, the current speed is stored and the cruise control function continues.
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If this position is selected for a shorter time than 300 ms, the requested speed is decreased by 1.6 km/h (1 mph).
SET/+
At the end of the direction indicator stalk switch, there is a spring-loaded pushbutton. When the button is pressed, connection B will be energized. This position has two functions:
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1.
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Engage cruise control and store the current speed in memory irrespective of whether any other speed has previously been stored there.
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2.
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The speed increases if the button is pressed. Once the button is released, the current speed will be stored and cruise control continues.
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If the button is pressed for a shorter time than 300 ms, the requested speed is increased by 1.6 km/h (1 mph).
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Pedal switches, brake and clutch
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For function and actuation, see:
Switch, clutch, cruise control (133), EDC16
Switch, brake, cruise control (134), EDC16
For function and actuation, see:
Switch, brake lights (29), EDC16
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The diagnostic tool contains a menu that indicates the condition that has not been fulfilled if cruise control cannot be engaged. Another menu indicates the reason why cruise control was disengaged when it was last used.
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System reaction to a fault
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Cruise control will be blocked if a fault occurs on the input from the brake light switch.
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