Principles Of Operation

Speed Control

Principles of Operation

There are 2 types of speed control systems that are available on this vehicle. The vehicle can be equipped with a standard speed control system or the speed control with adaptive cruise control system.

Speed Control - Without Adaptive Cruise Control

Pressing and releasing the steering wheel speed control 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. If the respective button is pressed and held, the vehicle speed continues to accelerate or decelerate until the button is released.

Pressing and releasing the OFF switch, or switching the ignition switch to the OFF position, turns the speed control system off. Pressing the brake pedal puts the speed control system in the standby mode. Pressing the RESUME button when the speed control system is in the standby mode causes the vehicle to accelerate to the last set speed. The RESUME button does not function if the OFF button is pressed, the ignition switch is in the OFF position, 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 Panel Cluster (IPC) or message center is illuminated.

The speed control deactivator 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, then the PCM deactivates the speed control system. Under increased brake pedal effort, the 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 speed control switches in the steering wheel.

The inputs to the PCM are:

- Output Shaft Speed (OSS) sensor
- Speed control switches
- Stoplamp switch
- Speed control deactivator switch

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

- Speed control indicator lamp
- Throttle command

The 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 vehicle speed and the desired speed.

The PCM strategy uses the throttle control for smooth accelerations.

The PCM sends a serial message over the High Speed Controller Area Network (HS-CAN) to the IPC to command the speed control telltale to be turned on or off.

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

The speed control system provides self-diagnostics. The speed control system will disable operation and set a PCM DTC if it detects certain faults. The IPC does not indicate speed control faults with a telltale or message center message. Fault codes are logged by the PCM.

An Electronic Throttle Control (ETC) system fault also causes the speed 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 speed control system to deactivate:

- Transmission gear selector is put into a position other than D or OD
- 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)
- Speed control switch is pressed or stuck longer than 2 minutes

Speed Control - With Adaptive Cruise Control

NOTE: The speed control sensor is also known as the forward looking sensor.

Pressing and releasing the steering wheel speed control ON switch turns the speed control system on. The message center displays the message CRUISE ON RADAR READY. This notifies the driver that the system is ready and the vehicle can be accelerated to the desired speed. Pressing and releasing the SET+ switch, sets the vehicle's speed that will be stored in memory and the message center displays SET XXX MPH (XXX km/h).

There are 2 ways to change the set speed. The first way is to accelerate or brake to the desired speed and press and release the SET+ or SET- speed control switch until the desired set speed is shown on the message center. The second way is by tapping the SET+ or the SET- switch while in the set mode, increasing or decreasing the maintained vehicle speed by 1.6 km/h (1 mph) per tap. If the respective button is pressed and held, the vehicle speed continues to accelerate or decelerate until the button is released. The adaptive cruise control system may apply the brakes to slow the vehicle down to the new set speed. The set speed displays continuously in the message center while the adaptive cruise control system is active.

The green speed control indicator illuminates in the IPC if the adaptive cruise control is on and is not following a vehicle ahead, while the amber adaptive cruise control indicator illuminates in the IPC if the adaptive cruise control is on and is following a vehicle ahead or a vehicle enters the same driving lane.

When a vehicle ahead enters the same lane or a slower vehicle is ahead in the same lane, the vehicle speed adjusts automatically to maintain a preset distance gap. Pressing the steering wheel speed control gap switch (Left arrow --- Right Arrow), the distance can be decreased or increased from the vehicle ahead. There are 3 gap settings that display on the message center:

- GAP Left Arrow - Right Arrow
- GAP Left Arrow --- Right Arrow
- GAP Left Arrow ----- Right Arrow

After each ignition cycle, the default gap setting is set to GAP Left Arrow ----- Right Arrow, which is the largest distance gap from the vehicle ahead. The message center momentarily displays the preset gap each time the distance gap is set.

The distance gap can be overridden by pressing the accelerator pedal. The green speed control indicator illuminates in the IPC and the message CRUISE OVERRIDE displays in the message center. When the accelerator is released, the adaptive cruise control system returns to normal operation and the vehicle speed decreases to the set speed or a lower speed if following a vehicle ahead.

The vehicle maintains the distance gap to the vehicle ahead until:

- the vehicle ahead accelerates to a speed above the set speed.
- the vehicle ahead moves out of lane or out of view.
- the vehicle speed falls below 30 km/h (18 mph).
- a new gap distance is set.

The speed control sensor, which is a radar unit, determines the distance and relative speed of the vehicle that is in the path of travel. The Cruise-Control Module (C-CM) commands the ABS module, which controls the vehicle brakes, to automatically apply the brakes to slow the vehicle to maintain a safe distance to the vehicle in front. The C-CM communicates with the ABS module over the High Speed Controller Area Network (HS-CAN). The C-CM monitors the yaw rate signal from the ABS module and compares it to the yaw rate signal from the speed control sensor. The maximum braking, which is applied by the adaptive cruise control system, is limited and can be overridden by the driver applying the brakes. If the adaptive cruise control system determines that its maximum braking level will not be sufficient, then an audible warning tone sounds while the system continues to brake. The message center displays DRIVER INTERVENE, and the driver should take immediate action.

Pressing and releasing the OFF switch, or switching the ignition switch to the OFF position, turns the adaptive cruise control system off. The adaptive cruise control set speed memory is erased.

Pressing the brake pedal puts the adaptive cruise control system in the standby mode. Pressing the RESUME button, when the adaptive cruise control system is in the standby mode causes the vehicle to accelerate to the last set speed. The set speed continuously displays in the message center while the adaptive cruise control system is active. The RESUME button does not function if the OFF button is pressed, the ignition switch is in the OFF position, or if the current vehicle speed is below the minimum operational speed.

The speed control deactivator 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, then the PCM deactivates the speed control system. Under increased brake pedal effort, the deactivator switch opens and removes the voltage from the PCM input circuit, releasing the throttle.

The adaptive cruise control system does not function if the vehicle speed is below 30 km/h (18 mph). As the vehicle slows down during automatic braking, the adaptive cruise control system discontinues braking at 30 km/h (18 mph). At that speed, an audible alarm sounds and the DRIVER INTERVENE message displays in the message center. The automatic braking from the ABS module is released and the driver must take over the vehicle braking control. The ABS module estimates brake temperature by monitoring applied brake pressure over a period of time and sends a message to the C-CM when the estimated temperature is above a given threshold. This condition may happen in a hilly or mountainous driving terrain.

There are several conditions that might exist to cause the adaptive cruise control system to deactivate or prevent the system from activation. Some of the conditions have a message that is displayed in the message center. These conditions include:





If the speed control sensor or fascia cover is dirty or obstructed due to rainy or snowy conditions, the message center displays CRUISE RADAR BLOCKED. The surface of the radar and speed control sensor fascia cover should be cleaned of any debris, moisture, snow, ice or any obstruction.

Network Communication

The following adaptive cruise control system components communicate via the HS-CAN:

- C-CM
- PCM
- ABS module
- Instrument Panel Cluster (IPC)

While there are numerous messages internal to the adaptive cruise control system module, the following messages are utilized by the adaptive cruise control system in conjunction with outside systems:

CAN Module Communication Message Chart (Part 1):

CAN Module Communication Message Chart (Part 2):