Principles of Operation
Cruise Control
Principles of Operation
Pressing and releasing the ON switch turns the cruise control system on. Pressing and releasing the SET/ACCEL or COAST switch while the vehicle is traveling at the desired speed activates the cruise control system.
Tapping the ACCEL or the COAST switch while in the set mode, respectively, increases or decreases the maintained vehicle speed by 1.6 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 switching the ignition switch to the off position, turns the cruise control system off. Applying the brake pedal puts the cruise control system in the standby mode. Pressing the RES switch when the cruise control system is in the standby mode causes the vehicle to accelerate to the last set speed. The resume feature does not function if the off switch is pressed, the ignition switch is in the off position or if the current vehicle speed is less than the minimum operational speed.
The cruise control deactivator switch is provided as an additional safety feature. When the brake pedal is applied, a voltage signal from the stoplamp switch to the PCM deactivates the system. Under increased brake pedal effort the cruise control deactivator switch (integral to the stoplamp switch) opens up and removes the voltage input to the PCM.
The clockspring provides the electrical interface between the steering column wiring and the cruise control switches on the steering wheel.
The inputs to the PCM are:
- Stoplamp switch
- Output Shaft Speed (OSS) sensor
- Transmission Range (TR) sensor
- Cruise control switches
- Cruise control deactivator switch (integral to the stoplamp switch)
- Accelerator pedal position sensors
The outputs of the PCM are:
- Cruise control indicator (networked)
- Electronic Throttle Body (ETB)
The vehicle speed is controlled by the PCM through ETB. Cruise control electronics are contained entirely within the PCM. When the cruise control system is active, the PCM corrects for deviations in the actual vehicle speed by proportionally moving the throttle plate. The PCM modulates the throttle to minimize error between actual vehicle speed and the desired speed.
The PCM sends a message over the High Speed Controller Area Network (HS-CAN) to the IPC whenever the cruise control indicator should be turned on or off.
In the event of an off command or a deactivation request from any source, the cruise control system carries out a deactivation and immediately returns the throttle to the idle position.
The cruise control system provides self-diagnostics. The cruise control is disabled anytime an error is detected in the system. No IPC indicator or message center messages are displayed when faults occur. Fault codes are logged by the PCM.
An electronically-controlled throttle system fault also causes the cruise control system to be disabled and a warning indicator (wrench light) or a message center message is displayed.
Additionally, the following conditions can cause the cruise control system to deactivate:
- Transmission gear selector in a position other than D or OD
- Cruise control set speed is overridden with the accelerator pedal for a period longer than 5 minutes
- Vehicle speed loss from set speed of greater than 16 km/h (10 mph) occurs
- Vehicle speed falls below the minimum allowable limit of 40 km/h (25 mph)
- Cruise control switch is pressed or stuck longer than 2 minutes
- Park brake switch engaged