Cruise control

Cruise control

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 control module regulates the fuel quantity so that the desired speed is maintained.

If the vehicle speed is lower than the requested, the requested fuel quantity will be increased until the speed reaches a certain level. In the same way, the requested fuel quantity will be reduced until the speed reaches a certain level if it is higher than the requested.

The control module is programmed for cruise control even if cruise control is not fitted as original equipment. Retrofitting is therefore simple.

From switch pin	To control module pin	Connection designation in diagnostic tool	SWITCH POSITION
			Zero position	ON/OFF	SET/+	RESUME/-	CANCEL
8	41	A	0	1	0	0	0
10	81	B	0	1	1	0	1
9	22	C	0	1	0	1	1

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:

1.	Engages cruise control and stores the current speed in memory unless a speed is already stored there.

2.	Engages cruise control if the speed is stored in memory but cruise control was cancelled with CANCEL, the brake or the clutch.

3.	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.

If this position is selected for a shorter time than 500 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:

1.	Engage cruise control and store the current speed in memory irrespective of whether any other speed has previously been stored there.

2.	The speed increases if the button is pressed. Once the button is released, the current speed will be stored and cruise control continues.

If the button is pressed for a shorter time than 500 ms, the requested speed is increased by 1.6 km/h (1 mph).

The following conditions must be fulfilled before cruise control can be engaged:

1.	Change of status on the connector

2.	Clutch and brake pedal switches = 0

3.	Speed, wire from ABS >25 km/h.

4.	Speed, bus from MIU >25 km/h.

5.	Rapid deceleration = 0.

6.	No TCS active (Bus from TC/ABS).

7.	Gear ratio corresponds with one of the gears.

8.	Brake light switch and clutch/brake pedal switches simultaneously = 1 at some time during this driving cycle.

9.	Inputs A, B and C = 0 prior to switch being moved to ON/OFF.

10.	Cruise control engaged with switch.

Pedal switches, brake and clutch

When the brake or clutch pedal is depressed, the pedal switches will cut the power supply to the control module and cruise control will be disengaged.

Clutch switch (133)

The clutch switch is used by the control module to calculate the gear position with the help of other sensors.

Depressing the clutch pedal will cut the power supply to control module pin 61.

Clutch information is used by the control module to:

•	disengage cruise control

•	enable torque reduction for gear changing

•	calculate the current gear

Brake light switch (29)

When the brake pedal is depressed, the normally open pair of contacts in the brake light switch will close and B+ will be applied on control module pin 79.

Brake light information is used by the control module to:

•	disengage cruise control

•	limit fuel at idling speed

•	enable diagnosis of the speed signal.

Brake switch (134)

Depressing the brake pedal will cut the power supply to control module pin 21.

The brake light switch information is used by the control module to:

•	disengage cruise control

Diagnostics

•	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.

•	If the control module registers a plausibility fault in the brake light switch, DTC P0571 will be generated.

•	If the control module registers a plausibility fault in the clutch switches, DTC P0704 will be generated.

System reaction to a fault

•	A fault in the input from the brake light switch or the clutch switch will block cruise control.