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 between 40 km/h (25 mph) and the maximum limited vehicle speed. The cruise control system is controlled by the steering wheel mounted switches (ON, OFF, SET+, SET-, and RES), CPP switch (manual transmission), and the brake pedal. The steering wheel mounted switches are hardwired to the PCM.

The cruise control functions include:

- turning on the cruise control system.
- setting and maintaining the desired vehicle speed.
- accelerating the vehicle speed.
- coasting down to a lower speed.
- resuming the prior vehicle speed.
- turning off the vehicle cruise control system.

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.

Tapping the SET+ or the SET- 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 turning the ignition switch to the OFF position, turns the cruise control system off. Applying the brake pedal puts the cruise control system into the standby mode. Pressing the RES switch, which is the resume 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 CPP switch is used on vehicles equipped with a manual transmission. When the clutch pedal is applied with the 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 Instrument Cluster (IC) or message center is illuminated.

The cruise control deactivator switch is provided as an additional safety feature. Normally, when the brake pedal is applied, an electrical signal from the stoplamp circuit to the PCM deactivates the system. Under increased brake pedal effort, the cruise control deactivator switch opens and removes the voltage from the PCM input circuit, releasing the throttle.

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
- Cruise control switch(es)
- CPP switch
- Cruise control deactivator switch
- Stoplamp switch
- Accelerator pedal position sensor

The outputs of the PCM are:

- Cruise control indicator lamp
- Throttle command

For gasoline engines, the cruise control system throttle position is completely controlled by the PCM through the electronic-controlled throttle body. Cruise control electronics are contained entirely within the electronic throttle control subsystem.

When the cruise control system is active, the PCM corrects for deviations in the actual vehicle by proportionally moving the throttle plate. The PCM modulates the throttle to minimize error between the actual vehicle speed and the desired speed.

The PCM strategy uses the throttle control for smooth accelerations.

For diesel engines, the vehicle speed is controlled by the PCM through the electronic control fuel delivery system.

The PCM sends a serial message over the Controller Area Network (CAN) to the IC whenever the cruise control indicate is turned on or off.

In the event of an OFF command or a deactivation request from the cruise control deactivator switch, the cruise control system carries out a hard deactivation and immediately returns the throttle to the idle position.

The cruise control system provides self-diagnostics. 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 Electronic Throttle Control (ETC) system fault also causes the cruise control system to be disabled. In this case, an ETC system 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 transmission)
- Clutch pedal is pressed (manual transmission)
- 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 40 km/h (25 mph)
- Cruise control switch pressed or stuck longer than 2 minutes
- ABS Fault