Principles of Operation

Cruise Control

Principles of Operation

NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

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.

The cruise control functions include:

- turning the cruise control system on.
- setting and maintaining the desired vehicle speed.
- accelerating the vehicle speed.
- decelerating the vehicle speed.
- turning the vehicle cruise control system off.

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 either switch is pressed and held, the vehicle speed continues to accelerate (SET+) or decelerate (SET-) 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 clutch pedal (manual transaxle) puts the cruise control system into the standby mode. Pressing the RESUME switch when the cruise control system is in the standby mode causes the vehicle to accelerate to the last set speed. The RESUME switch does not function if the OFF switch is pressed or if the current vehicle speed is below the minimum operational speed.

Whenever the cruise control system is engaged and active, a cruise control icon on the Instrument Cluster (IC) is illuminated.

The clutch pedal cruise control deactivator switch is used 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.

When the brake pedal is applied, an electrical signal from the stoplamp switch is sent to the PCM to deactivate the cruise control system. The cruise control deactivator switch is provided as an additional safety feature. Under increased brake pedal effort, the cruise control 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 (except hybrid)
- Transmission Range (TR) sensor
- Cruise control switch(es)
- Clutch pedal cruise control deactivator switch (manual transaxle)
- Stoplamp switch
- Cruise control deactivator switch
- Accelerator pedal position sensor

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, 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 High Speed Controller Area Network (HS-CAN) to the IC whenever the cruise control indicator should be turned on or off.

For non-hybrid, 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 ABS module monitors brake pressure and also receives the stoplamp switch input from the SJB along the HS-CAN bus. A fault in the ABS module can disable the cruise control system.

The cruise control system provides self-diagnostics. The cruise control is disabled anytime an error is detected in the system. No IC 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 or a 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 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)
- Parking brake is applied
- Cruise control switch is pressed or stuck for longer than 2 minutes
- Traction control event
- ABS system fault