Part 2

Cruise Control Description and Operation (Adaptive Cruise)

Cruise Indicators and Messages

SERVICE RADAR CRUISE

The distance sensing cruise control module (DSCC) commands the display of the SERVICE RADAR CRUISE message in the driver information center (DIC) when it detects a malfunction in the Adaptive Cruise Control (ACC) System. The DSCC sends a request to the body control module (BCM) via the GMLAN serial data circuit to display the SERVICE RADAR CRUISE message in the DIC. The DIC displays the SERVICE RADAR CRUISE message when it receives a class 2 serial data request from the BCM. The SERVICE RADAR CRUISE is displayed in the DIC only when a diagnostic condition is present, the cruise switch is in On position, the vehicle speed is above 40 km/h (25 mph), and cruise is engaged or attempted to be engaged. When the message is displayed in the DIC the ACC system disengages. The DIC sounds an internal chime anytime it displays the SERVICE RADAR CRUISE message.

CRUISE NOT READY

The DSCC commands the display of the CRUISE NOT READY message in the DIC when ACC cannot engage due to a temporary condition. The ACC vehicle conditions that prompt the display of the CRUISE NOT READY message are temporary and do not require service. If no target is identified by the forward looking sensor (FLS) and cruise is attempted to be engaged, the CRUISE NOT READY message will be displayed in the DIC until the FLS is able to identify an accepted target. CRUISE NOT READY message is also displayed in the DIC when the DSCC is too hot and the brakes are too hot. The DIC sounds an internal chime anytime it displays the CRUISE NOT READY message.

CLEAN RADAR

The CLEAN RADAR message displays in the DIC when the DSCC detects a blockage of the FLS and cruise is engaged or attempted to be engaged. The FLS may be blocked by snow, ice, dirt, heavy rain or road spray. The DSCC commands the display of the CLEAN RADAR message via a GMLAN serial data circuit request to the BCM. The DIC displays the CLEAN RADAR message when it receives a class 2 serial data request from the BCM. When the CLEAN RADAR message is displayed in the DIC, safely park the vehicle and turn OFF the ignition. Clean the driver side front fascia lens to eliminate the blockage. It may be necessary to clean both the outside surface of the lens, the inside surface of the lens and the DSCC surface. Refer to Distance Sensing Cruise Control Maintenance for more cleaning information. It is important to turn the ignition OFF before cleaning any of the named surfaces. This is because the CLEAN RADAR message may still display in the DIC after cleaning the 3 surfaces. Cycling the ignition to OFF for 10 seconds is necessary to clear the CLEAN RADAR indicator if the indicator remains ON in the DIC. The DIC sounds an internal chime anytime it displays the CLEAN RADAR message. In rare instances, the target characteristics or a vertically misaligned FLS may trigger the activation of the CLEAN RADAR message in the DIC. Refer to Distance Sensing Cruise Control Aiming.

Cruise Engaged Indicator

The ACC engaged indicator is displayed in the head-up display (HUD) when the ACC is engaged by pressing the set/decrease switch. When the set/decrease switch is pressed by the driver, the BCM forwards the switch state to the engine control module (ECM) over the GMLAN serial data circuit. The ECM will use the switch input information from the BCM to determine the driver intended vehicle speed. The ECM communicates to the DSCC over the GMLAN serial data circuit the ACC engaged state and the driver selected speed. When the DSCC receives the ECM message indicating that ACC is active, the DSCC commands the display of the ACC engaged indicator via a GMLAN serial data message to the BCM. The HUD displays the ACC engaged indicator when it receives a class 2 serial data message from the BCM requesting the display. The driver may have to adjust the position of the HUD or the intensity of the display to see the information being displayed properly.

Set Speed

The ACC vehicle set speed is displayed at all times in the primary or secondary display of the HUD when ACC is engaged. The set speed is displayed in the primary HUD display for a few seconds after the initial engagement of ACC or a change in the set speed has just occurred. When, the set speed display time in the primary HUD display elapses, the set speed display is moved to the secondary HUD display. The set speed is also moved to the secondary display when a new ACC related message needs to be displayed. The DSCC set speed display request is sent to the BCM via the GMLAN serial data circuit. The HUD displays the set speed when it receives a class 2 message from the BCM requesting the set speed displayed in the HUD. The HUD controls when the set speed is displayed in the primary or secondary HUD display.

Follow Distance

The HUD displays the driver selected following distance when ACC is engaged and the gap up/down switch is active. The current follow distance setting is displayed in the HUD for a few seconds after the gap up/down switch is pressed to increase or decrease the following distance. The DSCC follow distance display request is sent to the BCM via the GMLAN serial data circuit. The HUD displays the follow distance when it receives a class 2 message from the BCM requesting the follow distance displayed in the HUD. The HUD will not display the follow distance if an indicator with a higher priority needs to be displayed in the HUD.

CRUISE SPEED LIMITED

The CRUISE SPEED LIMITED indicator displays in the HUD when the DSCC detects that the ACC vehicle is travelling at a speed outside the operational range of the FLS and the vehicle speed is being reduced below the driver set speed. The DSCC limits the vehicle speed in order to stay within the acceptable speed limitations of the FLS. The DSCC also limits the vehicle speed in order to adjust the vehicle speed for the chosen gap switch setting. The high speed limit of the ACC system is 186.7 km/h (116 mph). The DSCC requests the display of the CRUISE SPEED LIMITED indicator via a GMLAN serial data message to the BCM. The HUD displays the CRUISE SPEED LIMITED indicator when it receives a class 2 serial data message from the BCM. With a maximum following distance setting, the maximum operating speed will be limited to 160.9 km/h (100 mph). Selecting a smaller following distance will allow greater operating speeds up to a maximum of 186.7 km/h (116 mph).

Vehicle Ahead Indicator

The vehicle ahead indicator is displayed in the HUD when the FLS identifies an in-path vehicle. The vehicle ahead indicator is a warning to the driver that a vehicle is ahead within a distance of 100 meters (109.3 yards). The indicator also serves as a feedback to the driver that the FLS is functioning properly. The DSCC commands the display of the vehicle ahead indicator via a GMLAN serial data message to the BCM. The HUD displays the vehicle ahead indicator when it receives a class 2 serial data message from the BCM. The vehicle ahead indicator only displays with ACC active and may sometimes display for stationary road objects.

TIGHT CURVE

The TIGHT CURVE indicator is displayed in the HUD when the DSCC reduces the vehicle speed for a curve in the road. The tight curve situation exists when the curve of the road extends outside the field of view of the FLS such that the FLS cannot see 100 meters (109.3 yards) ahead. The degree to which the vehicle speed is reduced depends on the extent the curve on the road reduces the usable range of the FLS field of view. In a tight curve situation, the ACC vehicle speed may be reduced even when there is a target vehicle in the path of the ACC vehicle. The DSCC uses an internal algorithm to control the vehicle speed to the radius of the curvature of the road. The DSCC requests the display of the TIGHT CURVE indicator via a GMLAN serial data message to the BCM. The HUD displays the TIGHT CURVE indicator when it receives a class 2 serial data message from the BCM. Since the TIGHT CURVE indicator is only displayed when the vehicle speed is reduced for a curve, the driver may notice a delay between entering the curve and the display of the TIGHT CURVE indicator.

Driver Alert

The driver alert indicator warns the driver of a certain road or vehicle conditions that require his attention. When the driver alert indicator flashes in the HUD it is accompanied by an audible warning from the audio amplifier. The driver alert indicator flashes in the HUD and the audible warning sounds when one of the following occurs:

* The DSCC is requesting maximum automatic braking.
* The DSCC automatic braking request is not sufficient to safely stop the vehicle in certain road conditions.
* Cruise disengagement not initiated by driver or any driver action.
* The vehicle speed is below 32 km/h (20 mph).
* Abnormal cruise disengagement

The DSCC requests the driver alert indicator and the audible warning via a GMLAN serial data message to the BCM. The BCM then sends a class 2 message to the HUD and to the audio amplifier requesting the driver alert indicator and the audible warning to be activated.

Cruise Engaged

The adaptive cruise control (ACC) system will engage and adjust vehicle speeds based on the activation of the following cruise switches:

* On/Off
* Set/Decrease
* Resume/Increase

ACC will not engage if any inhibit criteria is active. Also, the driver must step on the brakes at each ignition cycle before attempting to engage ACC. The engine control module (ECM) looks to the body control module (BCM) for the brake initial travel achieved signal indicating that the driver has stepped on the brakes before attempting to engage ACC.

The vehicle speed must be above 40 km/h (25 mph) and below 188.3 km/h (117 mph) for the ACC system to be engaged. In the engaged state, the ACC system allows the driver to override the controlled vehicle speed temporarily while still remaining in the engaged state.

Cruise Inhibited

DSCC Inhibits

The distance sensing cruise control module (DSCC) inhibits the adaptive cruise control (ACC) system when any of the following conditions exists:

* RADAR NOT READY message active in the driver information center (DIC)
* Initial brake pedal travel signal from brake pedal position sensor (BPPS) not present
* ACC system malfunction and/or failure and SERVICE RADAR CRUISE indicator active in the DIC
* CLEAN RADAR indicator active in the DIC
* Invalid vehicle speed
* Invalid yaw rate data from EBCM
* Invalid acceleration data from EBCM
* ABS active during automatic braking
* Cruise Switch failed message from the body control module (BCM) to the DSCC
* Automatic braking failure - GMLAN signal from ABS to DSCC indicating automatic braking failure
* Brakes overheated signal from Antilock Brake System (ABS)
* Head-up display (HUD) failure
* ACC system audible warning not present due to audio amplifier failure
* FLS temperature hot
* ACC is not present. ACC can be disabled through the BCM ACC disable feature.
* Driver applied brake pressure
* Cruise switch OFF

ECM Inhibits

The engine control module (ECM) inhibits the ACC system operation when any of the following conditions exists:

* ACC inhibited signal from DSCC is present.
* Vehicle speed drops below 32.2 km/h (20 mph).
* Vehicle speed is above 193.1 km/h (120 mph).
* Automatic braking failure - GMLAN signal from ABS to ECM indicating automatic braking failure
* ACC present signal from BCM is false.
* Driver applied brake pressure.
* Cruise Control switch failure
* Park brake switch signal from BCM is active.
* Electronic throttle control (ETC) failure
* Traction control is active.
* ABS is active.
* Engine overspeed protection is active.
* Vehicle overspeed protection is active.
* Engine speed is too high or too low.
* Automatic transmission is in First gear, Park, Neutral or Reverse.
* Initial brake pedal travel signal from BPPS not present
* System voltage is low.

Cruise Disengaged

The Adaptive Cruise Control (ACC) System disengages when any of the following occurs:

* The driver depresses the brake pedal.
* The driver turning the ACC On/Off switch OFF

Pressing the brake pedal while ACC is engaged will disengage the ACC System.

Other Adaptive Cruise Control (ACC) Features

Automatic Alignment

The Adaptive Cruise Control (ACC) System is equipped with an internal forward looking sensor (FLS) automatic horizontal alignment feature. This feature can not be used for vertical alignment. For proper operation of the ACC System, the FLS must be well aligned to the vehicle. The FLS alignment to the vehicle is continuously corrected and adjusted as necessary during the ACC vehicle operation. To achieve a complete automatic FLS alignment, the ACC vehicle has to be driven on a road above 56 km/h (35 mph) with acceptable stationary objects like mail boxes, road signs, trees, ramps and poles etc. The distance that the vehicle needs to be driven to achieve a complete automatic alignment, depends on the number of stationary objects encountered on the road that the vehicle is travelling. The more stationary objects encountered, the quicker the FLS will achieve automatic alignment. At least 40 acceptable stationary objects must be encountered for proper alignment. When the distance sensing cruise control module (DSCC) is replaced with a new module, it is necessary for the vehicle to be driven until the internal automatic alignment is complete. The scan tool is equipped to display the automatic alignment status and the degree of alignment error or skew of the FLS. A DTC C1002 sets in the DSCC when the degree of error or skew is 2.5 degrees or over.

It is important when performing a wheel alignment service on a vehicle equipped with the ACC System, to change the Auto Alignment Learn Status parameter in the DSCC scan tool data list to Not Aligned. The Auto Alignment Learn Status parameter of the DSCC needs to read Not Aligned to allow the FLS to automatically align to the vehicles new wheel alignment setting. Driving the vehicle in an area with stationary objects will cause the FLS to automatically align horizontally to the vehicles new wheel alignment setting.

Mechanical Alignment

Mechanical alignment must be used for vertical alignment. Proper vertical alignment is achieved with a bubble level tool rested against the front face of the FLS, with the bubble centered. When the alignment of the FLS is not achieved, an out of alignment diagnostic, DTC C1002 is set by the DSCC. The typical horizontal alignment value of the FLS is 0-2 degrees, but it is highly recommended to be as close to 0 degrees as possible. The DSCC diagnostic, DTC C1002 sets when at least 2.5 degrees of skew or error of the FLS is present. Refer to Distance Sensing Cruise Control Aiming for more information on how to aim and align the FLS. An out of alignment condition may be as a result of tampering or damage to the FLS, the FLS mounting structures or the FLS adjuster settings. An out of alignment condition may also be as a result of damage to the front end of the vehicle or merely as a result of wear and tear. Refer to Distance Sensing Cruise Control Module Replacement and Cruise Control Vehicle Distance Module Sensor Replacement on how to properly locate and mount the ACC module and the FLS.