Principles Of Operation
The speed control system is controlled by the speed control actuator.
The speed control actuator communicates through the standard corporate protocol (SCP) communications network with other modules. The SCP inputs to the speed control are vehicle speed, brake pedal ON/OFF, throttle position, RPM and PRNDL status. The SCP outputs from the speed control to the instrument cluster are system ON, OFF, engaged or disengaged.
The speed control actuator is controlled by the steering wheel-mounted switches (ON, OFF, SET+, SET-, and RES), and the brake pedal. The steering wheel-mounted switches are illuminated.
Pressing and releasing the ON switch turns the system on and puts the system in standby mode. Pressing and releasing the SET+ switch while the vehicle is traveling at the desired speed engages the system. The vehicle maintains the desired speed.
Tapping the SET+ or SET- switches, while in the set mode respectively, increases or decreases the maintained vehicle speed by 1.68 km/h (1 mph) per tap. If the respective switch is pressed and held, the vehicle speed continues to accelerate or decelerate until the switch is released.
Pressing and releasing the OFF switch, or positioning the ignition switch in the OFF position, turns the speed control off. Applying the brake pedal puts the system in the STANDBY mode. Pressing the RES switch, when the system is in the STANDBY mode, causes the vehicle to accelerate until the last set speed is resumed. Resume does not function if the OFF switch is pressed, the ignition switch is in the OFF position, or if the current vehicle speed is below the minimum operational speed.
Whenever the speed control system is engaged and active, a speed control indicator, located in the instrument cluster, is turned on.
The inputs to the speed control actuator for the speed control system are the:
speed control deactivator switch
smart junction box (SJB)
speed control switches
vehicle speed from the anti-lock brake system (ABS) module over the SCP communications network
throttle position status over the SCP communications network
stoplamp switch status over the SCP communications network
PRNDL status over the SCP communications network
The outputs from the speed control actuator are the:
instrument cluster indicator over the SCP communications network
speed control cable-controlled throttle position
The speed control system operates in the following modes:
When the speed control system is in the ON or STANDBY mode, and receives a SET+ switch input, the speed control maintains present vehicle speed (provided the vehicle speed is within the operating speed range). When the speed control system receives a constant SET+ switch input, the speed control system will accelerate the vehicle. The speed control system continues to accelerate the vehicle until the SET+ switch is released. If the duration of the SET+ switch input is less than 640 ms, it is considered a TAP UP and the speed control system will increase vehicle speed by 1.68 km/h (1 mph). When the system is in the STANDBY mode and a RES switch input is received, the speed control system modifies vehicle speed to resume the last SET vehicle speed, provided that the speed control system had previously been in the SET mode.
When the speed control system receives a constant SET- switch input, the speed control system will decrease the vehicle speed. Once the SET- switch is released, the speed control system maintains the present vehicle speed. If the duration of the SET- switch input is less than 640 ms, it is considered a TAP DOWN and the speed control system will decrease vehicle speed by 1.68 km/h (1 mph).
A hard deactivation occurs only under hard braking conditions and when the speed control deactivator switch is activated (open). This will immediately return the throttle to the idle position. All other speed control system deactivations are considered soft deactivations, returning the throttle to idle slowly.
Saturday, March 7th, 2009 AT 8:10 AM