Principles Of Operation

Cruise Control

Principles of Operation

The cruise control system is controlled by the PCM. The cruise control system is designed to maintain a selected vehicle speed above 37 km/h (23 mph) to the maximum limited vehicle speed. The cruise control system is controlled by the steering wheel mounted switches, the stoplamp switch, the clutch pedal cruise control deactivator switch (manual transaxle), and the cruise control deactivator switch (part of the stoplamp switch). The steering wheel mounted switches are hardwired to the PCM through the clockspring.

Pressing and releasing the ON switch turns the cruise control system on. Pressing and releasing the SET+ or SET- switch while the vehicle is traveling at the desired speed activates the cruise control system.

For early build vehicles, the cruise control indicator in the Instrument Panel Cluster (IPC) illuminates when the system is engaged. For late build vehicles, the cruise control system has 2 indicators in the IPC. The cruise control amber indicator illuminates when the system is on. The cruise control green indicator illuminates when the system is engaged.

Tapping the SET+ or the SET- switch while in the set mode 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 or the clutch pedal (manual transaxle) puts the cruise control system into the standby mode. Pressing the RESUME or RSM switch when the cruise control system is in the standby mode causes the vehicle to accelerate to the last set speed. 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.

The clutch pedal cruise control deactivator switch is incorporated on vehicles equipped with a manual transaxle. When the clutch pedal is applied with the vehicle cruise control system engaged, the normally closed switch opens and signals the PCM to deactivate the cruise control.

Whenever the cruise control system is engaged and active, a cruise control icon on the IPC is illuminated.

The cruise control deactivator switch (part of the stoplamp switch) is provided as an additional safety feature. When the brake pedal is pressed, an electrical signal is sent from the stoplamp switch to the PCM to deactivate the cruise control system. The PCM sends a message to the IPC and the illuminated cruise control icon is turned off. Under increased brake pedal effort, the deactivator switch opens and removes the voltage signal from the PCM input circuit, deactivating the cruise control system.

The clockspring provides the electrical interface between the steering column wiring and the cruise control switches in the steering wheel.

The inputs to the PCM are:

- Output Shaft Speed (OSS) sensor
- Digital Transmission Range (TR) sensor (automatic transaxle)
- Cruise control switch
- Clutch pedal cruise control deactivator switch (manual transaxle)
- Cruise control deactivator switch (part of the stoplamp switch)
- Accelerator pedal position sensor
- Parking brake

The outputs of the PCM are:

- Cruise control indicator lamp
- Throttle command

The cruise control system throttle position is completely controlled by the PCM through the electronically controlled throttle body. Cruise control electronics are contained entirely within the PCM.

For non-hybrid vehicles, 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 and desired vehicle speed. The PCM strategy uses the throttle control for smooth accelerations.

For hybrid vehicles, when the electric traction motor is powering the vehicle and the cruise control is active, the electronic actuator corrects for deviations in the actual vehicle speed by proportionally applying wheel torque. The control electronics modulate the wheel torque to minimize error between the actual vehicle speed and the desired speed.

The PCM sends a message over the Controller Area Network (CAN) to the IPC whenever the cruise control indicator should be turned on or off.

For non-hybrid vehicles, 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.

For hybrid vehicles, in the event of an off command or a deactivation request from any source except a brake pedal tap, the system carries out a hard deactivation and immediately returns control to the accelerator pedal.

The cruise control system provides self-diagnostics. 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 Electronic Throttle Control (ETC) system fault also causes the cruise control system to be disabled. In this case, an ETC system warning indicator or message center message is displayed.

Additionally, the following conditions cause the cruise control system to deactivate:

- Transmission gear selector in a position other than D or OD (automatic transaxle)
- Vehicle clutch pedal is applied (manual transaxle)
- Cruise control set speed is over-ridden 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 37 km/h (23 mph)
- Cruise control switch is pressed or stuck for longer than 2 minutes
- ABS fault