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 turned to "ON", the control module sends the information "CRUISE lamp ON" out on the bus. The main instrument unit then turns on the lamp.

When the "SET" button is subsequently pressed, the control module stores the current speed in the memory, provided that the other conditions for the cruise control function are fulfilled.

The control module then reads from a table that gives the normal rolling resistance on level ground at different speeds. The requested (stored) speed has now been converted to a requested driving wheel torque.

The requested driving wheel torque is then compared with the gear engaged and converted into the requested engine torque.



The requested engine torque is converted to the requested air mass/combustion and comprises the input signal from the cruise control system to the air mass control.

If the speed of the vehicle is lower than that requested, the requested air mass/combustion will be increased until acceleration reaches a certain level. Similarly, the requested air mass/combustion will be reduced until deceleration reaches a certain level if the speed of the vehicle is higher than that requested.

The control module is programmed for cruise control even if cruise control is not originally fitted. This facilitates subsequent fitting as an accessory.

From switch pin	To control module pin	Connection designation in diagnostic tool	SWITCH POSITION
			Zero position	ON/OFF	SET/+	RES/-	CANCEL
8	52	A	0	1	0	0	0
10	5	B	0	1	1	0	1
9	30	C	0	1	0	1	1

Zero position

The switch is spring-loaded to the neutral position. None of the switch connections A, B or C is live.

ON/OFF

When the switch is moved to the far left, connections A, B and C are supplied with current. The ON/OFF position has two functions, alternately ON and OFF.

CANCEL

Between the neutral position and ON/OFF, switch connections B and C are supplied with current. The position has the same function as pressing the brake or clutch pedal, i.e. the cruise control is disengaged but the set speed is retained in the memory.

RES/-

When the switch is moved to the far right from the neutral position, connection C is supplied with current. The position has three functions:

1.	Engages the cruise control and stores the current speed in the memory if no speed has already been stored there.

2.	Engages the cruise control if a speed is stored in the memory but the cruise control function has been disengaged with CANCEL, the brake pedal or the clutch pedal.

3.	If the position is selected while the cruise control is active, the speed will be reduced. When the control returns to the neutral position, the current speed will be stored and the cruise control function continues.

If the position is selected in less than 300 ms, the requested speed will be reduced by 1.6 km/h (1 mph).

SET/+

At the end of the direction indicator stalk is a spring-loaded pushbutton. When this button is pressed in, current is supplied to connection B. The position has two functions:

1.	Engages cruise control and stores the current speed in the memory regardless of whether another speed is already stored in the memory.

2.	With the button pressed in, vehicle speed increases. When the button is released, the current speed is stored and the cruise control function continues.

If the button is pressed in for less than 300 ms, the requested speed will be increased by 1.6 km/h (1 mph).

The following conditions must be fulfilled for the cruise control to be activated:

1.	Brake light switch = 0

2.	Clutch and brake pedal switches = 0

3.	Speed, lead from ABS >40 km/h.

4.	Speed, bus from MIU >40 km/h.

5.	Rapid speed reduction = 0.

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

7.	Manual gearbox: Gear ratio corresponds with one of the gears. Automatic transmission: D, 3, 2 or 1.

8.	Brake light switch, clutch pedal switch and brake pedal switch simultaneously = 1 at some time during this drive cycle.

9.	No diagnostic trouble code for throttle control blocking.

10.	Inputs A, B and C = 0 before the switch is moved to ON/OFF.

11.	Cruise control is activated by the switch.

Brake and clutch pedal switches

When the brake or clutch pedal is depressed, the pedal switches will cut the power supply to control module pins 29 and cruise control will be disengaged. On cars with automatic transmission, the circuit is powered from the gear selector position sensor in positions D, 3, 2 and 1. The pedal switches are works-fitted on all cars with manual gearbox, even those without cruise control.

Brake light switch

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 63.

Brake light information is used by the control module to:

•	disengage cruise control

•	enable engine torque limitation

•	enable diagnosis of the speed signal.

Diagnostics

•	The diagnostic tool contains a menu that shows the conditions that have not been fulfilled if the cruise control cannot be activated. Another menu shows why the cruise control was disengaged when it was last used.

•	If the input from the brake light switch is continuously B+, diagnostic trouble code P1576 will be generated. If the input from the brake light switch is continuously 0V, diagnostic trouble code P1577 will be generated.

System reaction to a fault

•	Cruise control will be blocked if a fault occurs on the input from the brake light switch.