Cruise Control: Description and Operation

SPEED CONTROL

See the Tribute Wiring Diagram for schematic information.

Principles of Operation

NOTE:The Smart Junction Box (SJB) is also know as the Generic Electronic Module (GEM).
The speed control system is controlled by the PCM. The speed control system is designed to maintain a selected vehicle speed between 48 km/h (30 mph) and the maximum limited vehicle speed. The speed control system is controlled by the steering wheel mounted switches (ON, OFF, SET+, SET-, and RESUME), clutch pedal cruise control deactivator switch (manual transaxle), and the brake pedal. The steering wheel mounted switches are hardwired to the PCM.It is normal for the engine RPM to increase slightly and then drop off slowly when the clutch pedal is applied during operation.The speed control functions include:

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

Pressing and releasing the ON switch turns the speed control system on. Pressing and releasing the SET+ or SET- switch while the vehicle is traveling at the desired speed activates the speed control system.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, respectively. 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 speed control system off. Applying the brake pedal or clutch pedal (manual transaxle) puts the speed control system into the standby mode. Pressing the RESUME switch when the speed 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 speed control system is engaged and active, a speed control icon on the Instrument Cluster (IC) is illuminated.The clutch pedal speed control deactivator switch is used on vehicles equipped with a manual transaxle. When the clutch pedal is applied with the vehicle speed control system engaged, the normally closed switch opens and signals the PCM to deactivate the speed control.
When the brake pedal is applied, an electrical signal from the stoplamp switch is sent to the PCM to deactivate the speed control system. The speed control deactivator switch is provided as an additional safety feature. Under increased brake pedal effort, the speed control deactivator switch opens and removes the voltage signal from the PCM input circuit, deactivating the speed control system.The clockspring provides the electrical interface between the steering column wiring and the speed control switches in the steering wheel.
The inputs to the PCM are:

- Output Shaft Speed (OSS) sensor
- Transmission Range (TR) sensor
- Speed control switch(es)
- Clutch pedal speed control deactivator switch (manual transaxle)
- Stoplamp switch
- Speed control deactivator switch
- Accelerator pedal position sensor

The outputs of the PCM for the speed control system are:

- Speed control indicator lamp
- Throttle command

The speed control system throttle position is completely controlled by the PCM through the electronically controlled throttle body. Speed control electronics are contained entirely within the PCM.When the speed 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.The PCM sends a message over the High Speed Controller Area Network (HS-CAN) to the IC whenever the speed control indicator should be turned on or off.In the event of an OFF command or a deactivation request from any source, the speed control system carries out a deactivation and immediately returns the throttle to the idle position.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 speed control system.The speed control system provides self-diagnostics. The speed control is disabled anytime an error is detected in the system. No IC telltale 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 speed control system to be disabled and a warning telltale (wrench light) or a message center message is displayed.Additionally, the following conditions cause the speed control system to deactivate:

- Transmission gear selector in a position other than D or OD (automatic transaxle)
- Vehicle clutch pedal is applied (manual transaxle)
- Speed 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 40 km/h (25 mph)
- Parking brake is applied
- Speed control switch is pressed or stuck for longer than 2 minutes
- Traction control event
- ABS system fault