Master & Steering Wheel Switches/ECM/BP Sensor & Operation

Cruise Control System Control Diagram:

Cruise Control

General
Cruise control functionality is fully integrated into the ME 7.2 ECU and uses electric throttle intervention to automatically maintain a set vehicle speed. Once engaged, the system can also be used to accelerate the vehicle without using the accelerator pedal. the cruise control system Consists of:

- Cruise control master switch
- +/- Speed switch
- Resume switch
- EMS ECU
- Electric throttle.

the Controller Area Network (CAN) bus is used by the cruise control system for the exchange of data between the ECM, EAT ECU, DSC ECU and instrument pack.

Cruise control is enabled when the master switch is pressed. Once enabled the cruise control system is operated using the steering wheel switches. the steering wheel switches output a serial data stream to the ECM, the ECM then adjusts the electric throttle to maintain the vehicle at the set speed.

the cruise control warning lamp provides a visual indication of when the system is engaged.

Master Switch

the master switch controls a feed to the ECM to enable the system. the switch is a momentary contact push switch on the left hand steering wheel switch pack.

Steering Wheel Switches

the steering wheel switches SET+ and RES are non latching push switches that engage and disengage cruise control and adjust the set speed. While pressed, the switches supply a serial data stream to the ECM to adjust the set speed.

ECM

the ECM receives serial data from the steering wheel switches which are interpreted by the ECM to operate cruise control. the ECM also controls the output of a cruise engaged signal to the EAT ECU.

the ECM incorporates a software module and associated components to enable cruise control operation by direct control of the electric throttle. In addition to controlling the throttle the software module monitors hardwired and CAN bus inputs to the ECM and prevents or suspends cruise control operation when the vehicle is not in the correct driving configuration.

While the master switch is selected off, only the OFF message can be transmitted. When the master switch is selected on the power feed from the switch enables the interface switches to send either the SET or RESUME messages, depending on the inputs from the steering wheel switches and the cruise control status message from the CAN bus. When the master switch is first switched on, the output of the RESUME message is automatically inhibited until after the first engagement of cruise control.

When cruise control is engaged, the ECM outputs a signal on CAN to the EAT ECU to provide a cruise control engaged signal. the EAT ECU uses the signal to switch between normal and cruise control modes of operation.


Brake Pedal Sensor

Outputs from the brake pedal sensor are supplied to the ECM to enable the system to detect when the brakes are applied. the brake pedal sensor is a Hall effect sensor that produces two outputs. Both outputs should be 0 to 2 voltswhile the brake pedal is released. When the brake pedal is pressed the Brake Lamp Switch (BLS output increases to between 6 and battery volts the Brake Lamp Test Switch (BLTS) output increases to between 10 and battery volts.

Cruise Control Operation

Cruise control is operated from the steering wheel mounted switches. Switch symbols are market dependent! There are 4 switches for cruise control.

1 Cruise control ON/OFF switch (O/I)
2 Cruise control accelerate/tip-up switch (+)
3 Cruise control decelerate/tip-down switch (-)
4 Cruise control resume switch

the driver can enable cruise control at any time by pressing the ON/OFF (O/I) switch. Pressing this switch places the cruise control function into "stand by mode" and illuminates the instrument pack mounted cruise control lamp.

When in "stand by" mode pressing the "+","" or "RESUME" cruise switch once will activate the cruise control function and set the "set speed" equal to the current vehicle speed.

Note that the vehicle speed has to be greater than the minimum cruise control speed value of 26 km/hr (16 mph) for the cruise control function to operate. There is no maximum speed limit.

Once the cruise control function is active switch presses will have the following actions:

- Each "short" press on the "+" switch will cause the "set speed" to be increased by 1 km/hr (tip-up function)
- Each "short" press on the "-" switch will cause the "set speed" to be decreased by 1 km/h (tip-down function). Note that the "set speed" cannot be adjusted to lower than the minimum cruise control speed value
- A "continuous" press on the "+" switch will cause the vehicle to accelerate until the switch is released. the vehicle speed at the point the switch is released becomes the new "set speed"
- A "continuous" press on the "-" switch will cause the vehicle to decelerate until the switch is released. the vehicle speed at the point the switch is released becomes the new "set speed". Note that the "set speed" cannot be adjusted to lower than the minimum cruise control speed value
- A press on the "RESUME" switch when returned to "stand-by" mode will re-activate the cruise control function using the remembered "set speed".

Other aspects of the cruise control function are:

- Pedal over-ride function
- If the driver uses the accelerator pedal while cruise control is active, the "set speed" remains unchanged. Hence when the driver releases the accelerator pedal, the cruise control function will remain active and return the vehicle to the current "set speed"
- If the driver presses the "+" or "-" switches during pedal over-ride, the "set speed" will change to the actual vehicle speed when the switch is pressed.
- the cruise control function is not available in "low range". Note however, that if cruise control was active or in stand-by mode when low range was selected the cruise function will automatically return to stand-by mode when high range is re-engaged and the previous set speed is remembered.
- When in stand-by mode, pressing the "I/O" switch will disable the cruise control function, switch OFF the instrument pack mounted cruise control lamp and the "set speed" will be lost
- the cruise control function will change from "active" to "stand-by" modes if:
- the driver brakes
- the driver presses the "O/I" switch
- the driver moves from "D" to "N"
- the driver selects "low range"
- the DSC system activates above a defined level. This should be indicated to the driver by the instrument pack "DSC active" warning lamp.