Principles Of Operation
Cruise Control
Principles of Operation
There are 2 types of cruise control systems available. The vehicle can be equipped with a standard or adaptive cruise control system. For both standard and adaptive cruise control the systems are controlled by the steering wheel mounted switches (ON/OFF, SET, CNCL, RES and GAP [adaptive only]) that are integrated into the LH steering wheel switch, and by the brake pedal. The cruise control switches are hardwired to the Steering Column Control Module (SCCM). The SCCM (Steering Column Control Module) sends High Speed Controller Area Network (HS-CAN) messages to the PCM to control the cruise control system.
The clockspring provides the electrical interface between the steering column wiring and the cruise control switches in the steering wheel.
Cruise Control - Without Adaptive Cruise Control
The cruise control system is controlled by the PCM and the network messages of the cruise control switch inputs from the SCCM (Steering Column Control Module). The cruise control system is designed to maintain a selected vehicle speed between 30 km/h (18 mph) and the maximum limited vehicle speed.
The cruise control functions include:
- turning on the cruise control system.
- setting and maintaining the desired vehicle.
- accelerating the vehicle speed.
- coasting down to a lower speed.
- resuming the prior vehicle speed.
- turning off the cruise control system.
The cruise control steering wheel mounted switches are momentary contact switches that toggle up and down for the switch state. Pressing up (ON) and releasing the ON/OFF switch turns the cruise control system on. The cruise control indicator, located in the Instrument Panel Cluster (IPC), illuminates gray to indicate the cruise control system is in standby mode. Pressing up (SET+) or down (SET-) on the SET switch while the vehicle is traveling at the desired speed activates the cruise control system. The cruise control indicator illuminates green to indicate the cruise control system is active.
Pressing up or down on the SET switch while in the active mode increases or decreases the maintained vehicle speed by 1.6 km/h (1 mph) per press. If the respective switch is pressed and held, the vehicle speed continues to accelerate or decelerate until the switch is released.
Pressing down (OFF) and releasing the ON/OFF switch, or turning the ignition switch to the OFF position, turns the cruise control system off. While the cruise control system is active, applying the brake pedal or pressing the CNCL (CANCEL) switch puts the cruise control system into standby mode. The cruise control indicator illuminates gray while in standby mode. Pressing the RES (RESUME) switch when the cruise control system is in standby mode causes the vehicle to accelerate to the last set speed. The cruise control indicator illuminates green to indicate the system is activated. Resume does not function if the OFF switch is pressed, the ignition switch is cycled OFF, or if the current vehicle speed is below the minimum operational speed.
The cruise control deactivator switch is an additional safety feature. 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 ground signal from the PCM input circuit, releasing the throttle immediately deactivating the system.
The inputs to the PCM are:
- Digital Transmission Range (TR) sensor
- Cruise control switch(es) (networked from SCCM (Steering Column Control Module))
- Cruise control deactivator switch (integral to the stoplamp switch)
- Stoplamp switch
- Accelerator Pedal Position (APP) sensor
- Vehicle speed (networked from ABS module)
The outputs of the PCM are:
- Cruise control indicator lamp request (networked to the IPC (Instrument Panel Cluster))
- Electronic Throttle Body (ETB) command
The vehicle speed is controlled by the PCM through the Electronic Throttle Control (ETC) subsystem. The PCM strategy uses the throttle control for smooth accelerations.
In the event of an OFF switch command or a deactivation request from the deactivator switch, the cruise control system carries out a 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 IPC (Instrument Panel Cluster) indicator or message center messages are displayed when faults occur. Fault codes are logged by the PCM or SCCM (Steering Column Control Module).
An ETC (Electronic Throttle Control) system fault also causes the cruise control system to be disabled. In this case, an ETC (Electronic Throttle Control) system powertrain malfunction (wrench) warning indicator is displayed.
Additionally, the following conditions cause the cruise control system to deactivate:
- Transmission gear selector is put into a position other than D or OD
- 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 30 km/h (18 mph)
- Cruise control switch is pressed or stuck longer than 2 minutes
- ABS fault
Cruise Control - With Adaptive Cruise Control
The adaptive cruise control system functions much like the standard cruise control system. The adaptive cruise control system automatically adjusts the vehicle speed to maintain a set gap distance from the front of the vehicle and the vehicle in the same path of travel.
The adaptive cruise control steering wheel mounted switches are momentary contact switches that toggle up and down for the cruise control switch state. The adaptive cruise control switch inputs are networked over the High Speed Controller Area Network (HS-CAN) from the Steering Column Control Module (SCCM) to the PCM to control the adaptive cruise control system. Pressing and releasing the steering wheel cruise control ON/OFF switch turns the cruise control system on. The adaptive cruise control indicator located in the IPC (Instrument Panel Cluster) illuminates gray and the previous gap setting and SET graphic is displayed indicating the system is in standby mode. This notifies the driver that the system is ready and the vehicle can be accelerated to the desired speed. Pressing up (SET+) and releasing the SET switch sets the vehicle's speed and stores the set speed in memory. The adaptive cruise control indicator illuminates green and the message center displays the set speed and gap setting graphic.
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 cruise 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 displayed set speed by 1.6 km/h (1 mph) per tap. If the respective button is pressed and held, the displayed set speed continues to increase or decrease 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.
When the adaptive cruise control system is on and is following a vehicle ahead or a vehicle enters the same driving lane, a follow vehicle graphic is displayed in the message center.
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. A bar graph graphic with 4 preset distance gap settings are displayed in the message center. Pressing up (decrease) or down (increase) on the steering wheel cruise control gap switch increases or decreases the distance from the vehicle ahead. If all of the bars are illuminated, this is the longest gap setting. If only one bar is illuminated that is the shortest gap setting.
After each ignition cycle, the previous gap setting is remembered and the system is set to that gap setting.
The distance gap can be overridden by pressing the accelerator pedal. The follow vehicle graphic is not displayed in the message center and the GAP and set speed display turns gray. 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.
For a complete illustration of the adaptive cruise control indicators and graphic displays refer to the Owner's Literature.
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 the lane or out of view.
- the vehicle speed falls below 30 km/h (18 mph).
- a new gap distance is set.
The Cruise-Control Module (C-CM) contains a radar sensor unit that determines the distance and relative speed of the vehicle that is in the path of travel. The C-CM (Cruise-Control Module) commands the ABS module, which controls the brakes, to automatically apply the brakes to slow the vehicle to maintain a safe distance to the vehicle in front. The ABS module sends a network message to the Body Control Module (BCM) that an electronically controlled deceleration has occurred. The BCM (Body Control Module) sends a voltage signal to illuminate the stoplamps. The C-CM (Cruise-Control Module), ABS module, and the BCM (Body Control Module) communicate over the High Speed Controller Area Network (HS-CAN).
The ABS module monitors the yaw rate signal from the Restraints Control Module (RCM) over the HS-CAN (High Speed Controller Area Network) and compares it to the wheel speed and steering wheel angle signals. If the ABS module determines the yaw rate is invalid, the ABS module disables the adaptive cruise control. The message center displays the message COLLISION WARNING MALFUNCTION and/or ADAPTIVE CRUISE MALFUNCTION.
The vehicle is equipped with a collision avoidance system that uses the C-CM (Cruise-Control Module) radar sensor to detect vehicles ahead that are moving in the same direction as the vehicle with adaptive cruise control system. In the event of a collision risk, the driver is alerted by a series of red LED warning lights which is part of the Head Up Display (HUD) module, and an audible warning chime. For more information on the collision avoidance system, refer to Fire Suppression System. The maximum braking 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 to slow the vehicle and avoid collision, the Head Up Display (HUD) module flashes and an audible warning tone sounds while the system continues to brake. The driver must then take over the vehicle braking control.
Pressing and releasing the OFF switch, or switching the ignition to OFF, turns the adaptive cruise control system off. The adaptive cruise control set speed memory is erased.
Pressing the brake pedal or pressing the RES/CNCL switch puts the adaptive cruise control system in standby mode and the last set speed is displayed in the message center with a strike through. Pressing the RES/CNCL button when the adaptive cruise control system is in 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 RES/CNCL button does not function if the OFF button is pressed, the ignition is cycled OFF, or if the current vehicle speed is below the minimum operational speed.
The cruise control deactivator switch (which is integral to the stoplamp switch) is an additional safety feature. When the brake pedal is pressed, an electrical signal is sent from the stoplamp switch to the PCM deactivating the cruise control system. Under increased brake pedal effort, the cruise control deactivator switch opens and removes the ground signal from the PCM input circuit, releasing the throttle immediately deactivating the system.
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 automatic braking from the ABS module is released. The message CRUISE CONTROL [AUTOMATIC BRAKING TURNED OFF] is displayed in the message center. 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 (Cruise-Control Module) when the estimated temperature is above a given threshold. An alarm sounds and the adaptive cruise control system is deactivated until the estimated brake temperature within the ABS module returns to cooler operating conditions. This condition can happen in a hilly or mountainous driving terrain.
There are several conditions that can 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 C-CM (Cruise-Control Module) radar or front bumper cover is dirty or obstructed due to rainy or snowy conditions, the message center displays ADAPTIVE CRUISE SENSOR BLOCKED. Clean the surface of the radar and bumper fascia cover of any debris, moisture, snow, ice or obstruction.
Switching To Standard Cruise Control
The adaptive cruise control system has the capability for the driver to change from adaptive cruise control to standard cruise control. The LH 5 way steering wheel switch is used to switch from the adaptive cruise control system to standard cruise control system with in the message center. For information on selecting the standard cruise control in the message center, refer to Owner's Literature. Once the driver has selected the standard cruise control in the message center, the adaptive cruise control indicator is replaced by the standard cruise control indicator. The vehicle no longer responds to lead vehicles or automatic braking. Upon the next vehicle ignition cycle, the vehicle defaults back to the adaptive cruise control system.
Cruise Control Deactivation Event PIDs
The PCM has PIDs available, through the powertrain DataLogger, that show what caused the last cruise control deactivation. The PCM has 24 cruise control deactivation event PIDs, identified as CRUISEOFF_00 through 24. The most recent deactivation event is always listed in the event PID. These PIDs display what caused the cruise control deactivation to trigger and can be a very useful tool when trying to identify the cause of a deactivation trigger.