Cruise Control Description and Operation Conventional Cruise Control
Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at speeds above 40 km/h (25 mph). Steep grades may cause variations in the selected vehicle speeds.
The following are the main components of the Cruise Control System:
| • | The brake pedal position (BPP) sensor |
| • | The body control module (BCM) |
| • | The cruise control switches |
| • | The engine control module (ECM) |
| • | The throttle actuator control (TAC) motor |
| • | The vehicle speed sensor (VSS) |
Cruise Control Engaged
The Cruise Control System will engage and adjust vehicle speeds, based on the activation of the following cruise control switches, which are located on the steering wheel:
The body control module (BCM) monitors the signal circuit of the cruise control switches. The BCM relays the cruise control switch status to the engine control module (ECM) via the GMLAN serial data circuit. The ECM uses the status of the cruise control
switch to determine when to capture and maintain the vehicle speed. The ECM monitors the vehicle speed signal circuit in order to determine the desired vehicle speed. The ECM uses the throttle actuator control (TAC) motor in order to maintain the vehicle speed.
For further information on the TAC System, refer to
Throttle Actuator Control (TAC) System Description
.
Voltage is supplied to the cruise control switch from the steering wheel control switch reference voltage circuit supplied by the BCM. The cruise control switches are arranged in a resistive ladder design, with each cruise control function switch having
a different resistance value. The BCM detects a specific voltage value that is associated with the cruise control function switch being activated. When the normally open cruise control On/Off switch is turned ON, the switch closes and the BCM supplies a ground
to the cruise control switch ON indicator circuit as it becomes illuminated. The BCM sends a GMLAN serial data message to the ECM indicating that the On/Off switch is active. Similarly, when the normally open + RES switch or the normally open - SET switch
are pressed, the switch closes and the BCM detects the predetermined voltage signal on the - SET switch and the + RES switch signal circuit. The BCM sends a GMLAN serial data message to the ECM indicating that the + RES switch or the - SET switch
is active. To engage the Cruise Control System, ensure that the vehicle speed is above 40.2 km/h (25 mph), and then turn the On/Off switch ON and momentarily press the - SET switch. The ECM will engage the Cruise Control System and record the vehicle
speed. The ECM sends a GMLAN serial data message to the driver information center (DIC) in order to illuminate the CRUISE SET TO ### message. The ECM sends a GMLAN serial data message to the instrument panel cluster (IPC) in order to illuminate the Cruise Engaged
indicator in the IPC. The - SET switch and the + RES switch will remain inactive when the BCM has not received the predetermined voltage signal from the On/Off switch. Pressing the accelerator pedal, while the Cruise Control System is engaged, will allow
the driver to override the Cruise Control System in order to accelerate the vehicle beyond the current set vehicle speed. When the accelerator pedal is released, the vehicle will decelerate and resume the current set vehicle speed. The driver can also override
the current set vehicle speed via the - SET switch and the + RES switch. When the Cruise Control System is engaged, pressing and holding the - SET switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating
the Cruise Control System. When the - SET switch is released, the ECM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the Cruise Control System is engaged, momentarily pressing - SET switch will allow
the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the - SET switch is momentarily pressed, with a minimum vehicle speed of 37 km/h (23 mph). Pressing and holding the + RES switch, when the Cruise Control
System is engaged, will allow the vehicle to accelerate to a greater vehicle speed than the current set vehicle speed. When the + RES switch is released, the ECM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When
the Cruise Control System is engaged, momentarily pressing the + RES switch will allow the vehicle to accelerate at 1.6 km/h (1 mph) increments for each time that the + RES switch is momentarily pressed, with the maximum acceleration total of 16 km/h
(10 mph) over the current set vehicle speed. Momentarily activating the + RES switch will recall the previous vehicle speed, after the Cruise Control System is disengaged by pressing the brake pedal or by activating the CANCEL switch.
Cruise Control Disengaged
The engine control module (ECM) disengages the cruise control operation based on the signals from the following switches:
| • | The brake pedal position (BPP) sensor |
| • | The cruise control On/Off switch |
| • | The cruise control cancel switch |
The body control module (BCM) determines when the cruise control cancel switch is activated. When the normally open cancel switch is closed, the BCM detects the predetermined voltage signal on the cruise control function switch circuit. The BCM sends a
GMLAN serial data message to the ECM in order to disengage the cruise control system.
The BPP sensor is mounted on the brake pedal bracket. Pressing the brake pedal while the cruise control is engaged will disengage the Cruise Control system. The BCM monitors the BPP sensor signal circuit as the voltage signal increases, while the pedal
reaches the fully applied position. The BCM sends a GMLAN serial data message to the ECM indicating the position of the brake pedal. For more information on the BPP sensor, refer to
Exterior Lighting Systems Description and Operation
and to
Brake Pedal Position Sensor Calibration
.
The Cruise Control System will also disengage when one of the following conditions exist:
| • | The cruise control On/Off switch is switched OFF. |
| • | The ECM detects that a drive override function has been active for approximately 60 seconds. |
When the Cruise Control System has been disengaged, the ECM sends a GMLAN serial data message to the instrument panel cluster (IPC) in order to turn OFF the Cruise Engaged indicator, and to the drive information center (DIC) in order to turn OFF the CRUISE
SET TO ### message. The vehicle speed stored in the memory of the ECM will be erased when the cruise control On/Off button is turned OFF, or the ignition switch is turned OFF.
Cruise Control Inhibited
The engine control module (ECM) inhibits the cruise control operation when any of the following conditions exist:
| • | The ECM has not detected a brake pedal activation from the body control module (BCM). |
| • | A Cruise Control System DTC has been set. |
| • | The vehicle speed is less than 40.2 km/h (25 mph). |
| • | The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear. |
| • | The engine RPM is too low. |
| • | The engine RPM is too high. |
| • | The vehicle speed is too high. |
| • | The system voltage is not between 9-16 volts. |
| • | The Antilock Brake System (ABS)/Traction Control System (TCS) is active for more than 2 seconds. |
Cruise Control Description and Operation Adaptive Cruise Control
Adaptive Cruise Control (ACC)
The Adaptive Cruise Control System (ACC) is an enhanced Cruise Control System with the ability to sense and react to forward traffic. Compared to the common Cruise Control System found on many vehicles, the main functional enhancement of the ACC System
is the ability to detect the presence of a vehicle in the path of the ACC vehicle. The ACC retains the existing cruise control feature that controls the vehicle speed to the driver selected speed. However, ACC allows a driver to set and maintain a following
distance to the preceding nearest vehicle in the ACC vehicle path. The distance sensing cruise control (DSCC) module calculates a follow speed limit to ensure an acceptable distance is maintained to the preceding vehicle in front, should one be present. The
ACC System automatically adjusts the speed of an ACC vehicle when the vehicle comes up behind a slower travelling vehicle in front. The ACC System applies limited automatic braking and throttle control without driver input when necessary to maintain the set
following distance of the ACC vehicle. The preceding vehicle's speed and acceleration along with the ACC vehicle speed and acceleration and the distance between the 2 vehicles are factors used by the DSCC module to determine the ACC follow speed limit. The ACC
vehicle speeds up to the original driver selected set speed when the pathway becomes clear without driver input.
Adaptive Cruise Control (ACC) System Description
The Adaptive Cruise Control (ACC) System depends on various modules on the vehicle to function and each module performs a function that is critical to the proper operation of the ACC System. ACC will not operate if any components fail. Communication between
modules is via the high-speed GMLAN serial data circuit. The instrument panel module (IPM) provides a translating gateway function for the GMLAN serial data links. The GMLAN utilizes the controller area network (CAN) communications protocol. The following is
a functional description of the distance sensing cruise control (DSCC) module and the other associated components:
Distance Sensing Cruise Control (DSCC) Module
The DSCC module contains the radar and the DSCC controller. The DSCC module utilizes the radar to identify and classify objects in the road environment. The radar scans the road environment to detect targets within its specified field of view. The DSCC
controller then makes throttle and/or brake commands to the engine control module (ECM) and electronic brake control module (EBCM) via the GMLAN serial data circuit in order to control the vehicle acceleration/deceleration based on the data from the radar. The
ECM and EBCM provide throttle control and automatic braking needed for proper cruise speed adjustment. An internal yaw rate sensor is used by the DSCC module to determine the predicted path of the ACC vehicle. The main power feed for the DSCC module is the battery
and this signal is always at battery potential. However, the ACC System only activates when the ignition 1 input is active and in the RUN position. The ignition 1 voltage signal to the DSCC module has to be 9.2 volts or more to be considered
active by the DSCC module. When the ignition 1 signal is not active, all ACC functions are disabled. The following is a list of the DSCC module functions:
| • | The radar processes the road environment to get data concerning any vehicle ahead of the ACC vehicle. Detection, parameter estimation, tracking, object classification and diagnostics are the primary radar functions. When an object is detected, the
DSCC controller calculates the object range, range rate, acceleration and azimuth angle parameters. |
| • | The DSCC module performs ACC state processing automatically--distance control or speed control. The ACC System operates in 2 possible states--Cruise or Follow. The normal operating state is Cruise, whereby the vehicle speed is controlled
to match the driver selected set speed. When a preceding forward target is identified by the radar, the ACC System will automatically transition into the follow speed state to provide proper lane spacing behind the target vehicle in front. The preceding vehicle's
speed and acceleration, with the ACC vehicle speed, acceleration and distance between the two vehicles will be used to determine the ACC follow speed limit. The ACC follow speed limit will ensure that an acceptable distance is maintained to the preceding vehicle. |
| • | The DSCC module determines the follow speed limit for throttle control by the ECM. |
| • | The DSCC module arbitrates the ACC System brake and throttle control between the EBCM and the ECM. |
| • | The DSCC module requests brake light activation during automatic braking. |
| • | The DSCC module provides operational feedback to the vehicle driver. The DSCC module sends signals for telltales and messages to be displayed on the driver information center (DIC) via the IPM. The DSCC module will provide audible feedback to the
driver via the IPM and the radio amplifier as well. |
Instrument Panel Module (IPM)
The following are the ACC System functions provided by the IPM:
| • | The IPM provides a translating gateway for the high speed GMLAN serial data circuit. |
| • | The IPM reads all cruise control switches and the gap switch. The DSCC module monitors a variety of user operated switches from the IPM switch status information sent via the GMLAN serial data circuit. |
| • | The IPM illuminates the brake light based on a GMLAN message from the DSCC module during automatic braking. |
| • | The IPM measures the brake pedal position and sends brake pedal travel status via GMLAN serial data circuit to the ECM. The ECM disengages the ACC System when the brake is applied by the driver pressing the brake pedal. |
| • | The IPM serves as a gateway to the display systems, instrument panel cluster (IPC), DIC and amplifier, visual and audible warnings. The IPM will generate visual and audible warnings based on high speed GMLAN serial data messages from the DSCC module. |
Engine Control Module (ECM)
The following are the ACC System functions performed by the ECM:
| • | The ECM provides the electronic throttle control to the ACC System. The ECM is also responsible for determining when a driver is overriding the adaptive cruise control throttle position by pressing the accelerator pedal. |
| • | The ECM processes the cruise control switch requests received via the GMLAN serial data circuit from the IPM. Engaging and disengaging the ACC System are functions performed by the ECM. |
| • | The ECM determines the driver selected vehicle speed. Unless the ACC module requests a lower vehicle speed, the ECM will control the vehicle speed to the driver selected set speed. |
| • | The ECM allows automatic braking without disengaging the ACC. |
Antilock Brake System (ABS)
The following are the ACC System functions performed by the EBCM:
| • | The EBCM controls the operation of the Antilock Brake System. |
| • | The EBCM provides automatic braking for the ACC System. The DSCC module will request vehicle deceleration via high speed GMLAN serial data circuit. |
| • | The EBCM determines when the driver-applied brake pressure is active. The EBCM will communicate this status via the GMLAN serial data circuit to the IPM. |
| • | The EBCM releases vehicle automatic braking when there is a throttle override by the driver pressing the accelerator. |
| • | The EBCM predicts brake temperatures. Due to automatic braking, the brake system may overheat. When the brakes are overheated, the EBCM requests the ACC System to be temporarily shut down by the ECM until the brakes cool to a normal operating temperature. |
Refer to
ABS Description and Operation .
Transmission Control Module (TCM)
The transmission control module (TCM) provides a down shift to protect the brakes. When the TCM detects some driver braking activity or ACC automatic braking activity, the TCM down shifts the vehicle transmission to increase engine braking. This helps
reduce braking activity, extend brake pad life and reduce brake system overheating.
Driver Information Center (DIC)
The DIC is a part of the IPC and displays the ACC System warning messages. The DSCC module requests messages to be displayed on the DIC by sending a GMLAN request to the IPM. The IPM sends a GMLAN serial data request to the DIC demanding the display of
the warning message. When the message is acknowledged by the driver and the cause of the message resolved, the DIC turns the message off. These displays are accompanied by a chime warning internal to the DIC. The ACC System will not operate if the DIC fails.
The following are the 3 ACC messages that can be displayed on the DIC:
Radio Amplifier
The amplifier receives a GMLAN serial data message from the IPM in order to request an audible warning. The chime alerts the vehicle driver to certain ACC vehicle conditions. The audible chime accompanies a visual indicator as a warning to the driver.
The ACC System will not operate if the radio amplifier fails.
Brake Pedal Position (BPP) Sensor
The IPM monitors the brake pedal position (BPP) sensor in order to determine when pressure is being applied to the brake by the driver stepping on the brake pedal. The BPP sensor receives a low reference signal and a 5-volt reference from the IPM. When
the brake is applied, a signal is applied from the BPP sensor through the BPP sensor signal circuit to the IPM. The IPM utilizes this signal in deciding when to command the activation of the stop lamps. The IPM continuously sends signals via the GMLAN serial
data circuit to the EBCM and the ECM reflecting the brake pedal position status. This will include the initial brake travel signal required for the activation of the ACC System. The ACC System will not engage unless the initial brake pedal travel signal is valid
and received by the IPM. When the IPM brake pedal position signal indicates that brake pedal pressure is being applied by the driver when the ACC System is engaged, the ECM immediately disengages the ACC System. Re-engaging the ACC System will require the driver
pressing the set or resume switch. Refer to
Brake Pedal Position Sensor Calibration and to
Exterior Lighting Systems Description and Operation for more information on the brake pedal pressure sensor.
Accelerator Pedal
Deceleration of the ACC vehicle to maintain a certain distance and speed while a slower moving vehicle is in its path is achieved through throttle control by the ECM and the application of light automatic braking by the EBCM. During automatic braking the
ECM is commanded to release the throttle by the DSCC module. The DSCC module via the GMLAN serial data circuit requests the ECM to release the throttle from the currently controlled cruise position. At the end of automatic braking, the ECM will control the vehicle
speed to the current set vehicle speed. Driver throttle override occurs when the driver of the ACC vehicle depresses the accelerator pedal with the intention of requesting greater speed than the current throttle position. An example is an ACC vehicle driver
stepping on the accelerator for a passing maneuver. The ECM continuously monitors the throttle and reports a throttle override condition. When no throttle override is present, automatic braking is allowed. When throttle override is detected by the ECM, automatic
braking in not allowed to affect the vehicle acceleration.
Cruise Control Switch
The cruise control switch, functionally is a common feature that is shared between the Adaptive Cruise Control (ACC) System and the regular Cruise Control System. The ACC System will not operate if any cruise switch fails. The cruise control switch comprises
the following cruise control function switches:
The cruise control function switches are arranged in a resistive ladder design whereby each switch function is set up with different resistance values. The instrument panel module (IPM) through the cruise control switch signal circuit detects a predetermined
voltage value when any cruise control switch function is activated. The associated cruise control function signal detected by the IPM is then sent to the engine control module (ECM) as a GMLAN serial data circuit message. The ECM on receiving the message provides
the cruise control function requested by the IPM. The ECM is responsible for recognizing and responding to cruise control switch requests sent by the IPM. The cruise control function switches are used by the ECM to communicate to the distance sensing cruise
control (DSCC) module the driver selected vehicle speed. The driver selected vehicle speed is communicated through GMLAN serial data circuit to the DSCC module and the IPM. The ACC System engages and adjusts vehicle speeds based on the activation of the following
cruise control function switches:
On/Off Switch
The IPM monitors the cruise control set/coast and resume/accel switch signal circuit in order to determine when the On/Off switch is disabled or activated. The IPM detects a predetermined voltage value on the cruise control set/coast and resume/accel switch
signal circuit. The On/Off switch state is then relayed to the ECM via the GMLAN serial data circuit. The ECM sends the On/Off switch input status to the DSCC module. When the On/Off switch is turned ON, the ACC System enters either a standby enabled or a standby
disabled mode. The standby enabled mode indicates that every condition required for the ACC System to function has been met, but the ACC is not engaged. When the ACC is in the standby disabled mode, the conditions necessary for the ACC System to function has
not been met. When the On/Off switch is turned OFF, the ACC will enter the disabled mode. The ACC will not activate in the disabled mode. When the automatic braking is active and the ACC On/Off switch is turned OFF, the ACC will delay entering the disabled mode.
Set/Decrease Switch
The ACC System is engaged when the ACC On/Off switch is turned ON and the set/decrease switch is momentarily pressed and released. When the set/decrease switch is pressed, the selected vehicle speed is set to the current vehicle speed by the ECM. The vehicle
speed must be at or greater than 48 km/h (30 mph). While in the engaged state, the selected vehicle speed and the following distance can be adjusted. Pressing and holding the set/decrease switch, when the ACC System is engaged, will decrease the
selected vehicle speed without deactivating the ACC. Momentarily pressing and releasing the set/decrease switch, when the ACC is engaged, decreased the selected vehicle speed by 1.6 km/h (1 mph) for each time that the set/decrease switch is pressed.
Resume/Increase Switch
The resume/increase switch is used in order to increase the selected vehicle speed when ACC is active. The amount selected vehicle speed can be increased from the resume/increase switch depends on how long the switch is pressed. The presence of a slower
moving vehicle in the path of the ACC vehicle will limit the extent to which the selected vehicle speed can be achieved. If there is no preceding vehicle in front, limiting the ACC vehicle acceleration, then the vehicle speed that is attained is the new selected
vehicle speed. Acceleration is terminated when the resume/increase switch is released. Momentarily pressing and releasing the resume/increase switch will allow the selected vehicle to accelerate in at 1.6 km/h (1 mph) increments for each time that
the resume/increase switch is momentarily pressed.
Gap Up/Down Switch
The gap up/down switch allows the driver to determine how closely the adaptive cruise control (ACC) vehicle follows a target vehicle while ACC is engaged. When the ACC vehicle speed is being limited due to a slower travelling vehicle, the ACC vehicle speed
is automatically controlled to the follow speed limit. The gap switch has 6 following distance selections that range from 1-2 seconds. The gap switch following distance between the ACC vehicle and the target vehicle is expressed in time as opposed
to actual distance. The distance maintained for a selected gap will vary based on vehicle speed. The faster the vehicle speed, the further back you will follow. The gap setting can only be adjusted when the ACC System is engaged. The gap up/down switch is hard-wired
to the instrument panel module (IPM) and voltage is provided to the switch from the IPM via the gap up/down ignition 1 voltage circuit. Based on voltage variations, the IPM is able to read the selected gap up/down switch selection and communicates the switch
status on the GMLAN serial data circuit to the distance sensing cruise control (DSCC) module. The gap up/down switch is a 3 position momentary switch--Center, Gap Up and Gap Down--with the following valid signal values:
The initial push of the gap switch recalls the current setting and activates the display. Subsequent pushes of the gap switch will change the gap setting. Momentarily pressing the gap up/down switch will adjust the switch to the desired gap setting. When
the voltage from the gap up/down switch circuit is in an invalid range, the IPM will default to increasing the gap value.
Cruise Indicators and Messages
SERVICE RADAR CRUISE
The DSCC module 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 module sends a request to the instrument panel module (IPM)
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 GMLAN serial data message request from the IPM. The SERVICE RADAR CRUISE is displayed in the DIC only
when a diagnostic condition is present, the cruise switch is in the On position and the vehicle speed is above 48 km/h (30 mph). 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 module 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 radar at the time of vehicle ignition, the CRUISE NOT READY message will be displayed in the DIC until the radar is able to identify a target. CRUISE NOT READY message is also displayed in the DIC when the DSCC transceiver 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 module detects a blockage of the radar. The radar may be blocked by snow, ice, dirt, heavy rain or road spray. In rare instances, a vertically misaligned radar may trigger the activation of the
CLEAN RADAR message in the DIC. The DSCC module commands the display of the CLEAN RADAR message via a GMLAN serial data circuit request to the IPM. The DIC displays the CLEAN RADAR message when it receives a GMLAN serial data message request from the IPM. When
the CLEAN RADAR message is displayed in the DIC, safely park the vehicle and turn OFF the ignition. Clean the front fascia cover to eliminate the blockage. It may be necessary to clean both the outside surface of the cover, the inside surface of the cover and
the DSCC module 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 three 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. If the CLEAN RADAR indicator still remains ON after cleaning the radar and cycling the ignition, then
the radar alignment will need to be checked and verified. Perform the
Distance Sensing Cruise Control Aiming , if the radar is misaligned. The DIC sounds an internal chime anytime it displays the CLEAN RADAR message.
Cruise Engaged Indicator
The ACC engaged indicator is displayed in the driver information center (DIC) when the ACC is engaged by pressing the set/decrease switch. When the set/decrease switch is pressed by the driver, the IPM 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 IPM to determine the driver intended vehicle speed. The ECM communicates to the DSCC module over the GMLAN serial data circuit the ACC engaged state and the driver
selected speed. When the DSCC module receives the ECM message indicating that ACC is active, the DSCC module commands the display of the ACC engaged indicator via a GMLAN serial data message to the IPM. The HUD displays the ACC engaged indicator when it receives
a GMLAN serial data message from the IPM requesting the display.
Set Speed
The ACC vehicle set speed is displayed at all times in the DIC when ACC is engaged. The DSCC module set speed display request is sent to the IPM via the GMLAN serial data circuit. The DIC displays the set speed when it receives a GMLAN serial data message
from the IPM requesting the set speed displayed. The DIC controls when the set speed is displayed.
Follow Distance
The DIC 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 DIC for a few seconds after the gap up/down switch is pressed to increase or decrease
the following distance. The DSCC module follow distance display request is sent to the IPM via the GMLAN serial data circuit. The DIC displays the follow distance when it receives a GMLAN serial data message from the IPM requesting the follow distance displayed
in the DIC. The DIC will not display the follow distance if an indicator with a higher priority needs to be displayed in the DIC.
Vehicle Ahead Indicator
The vehicle ahead indicator is displayed in the DIC when the radar 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 radar is functioning properly. The DSCC module commands the display of the vehicle ahead indicator via a GMLAN serial data message to the IPM. The DIC displays the vehicle ahead indicator when it receives a GMLAN
serial data message request from the IPM. The vehicle ahead indicator only displays with the ACC active and may sometimes display for stationary road objects.
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 DIC it is accompanied by an audible warning from the audio amplifier. The driver alert indicator
flashes in the DIC and the audible warning sounds when one of the following occurs:
| • | DSCC module is requesting maximum automatic braking. |
| • | DSCC module automatic braking request not sufficient to safely stop the vehicle in certain road conditions. |
| • | Cruise disengagement not initiated by driver or any driver action. |
| • | Vehicle speed is below 32 km/h (20 mph) |
| • | Abnormal cruise disengagement |
The DSCC module requests the driver alert indicator and the audible warning via a GMLAN serial data message to the IPM. The IPM then sends a GMLAN serial data message to the DIC 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:
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 instrument panel module (IPM) 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 at or above 48 km/h (30 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 Module Inhibits
The distance sensing cruise control (DSCC) module inhibits the Adaptive Cruise Control (ACC) System when any of the following conditions exists:
| • | The RADAR NOT READY message is active in the driver information center (DIC). |
| • | Initial brake pedal travel signal from brake pedal position (BPP) sensor is not present |
| • | An ACC System malfunction and/or failure is present. |
| • | The CLEAN RADAR indicator is active in the DIC. |
| • | An invalid vehicle speed |
| • | The Antilock Brake System (ABS) is active during automatic braking. |
| • | The Cruise Switch failed message from the IPM is sent to the DSCC module. |
| • | Automatic braking failure--a GMLAN signal from the electronic brake control module (EBCM) the to DSCC module indicating an automatic braking failure |
| • | The brakes overheated signal from ABS |
| • | The ACC System audible warning is not present, due to an audio amplifier failure. |
| • | The DSCC module transceiver temperature is hot. |
| • | The ACC is not present--the ACC can be disabled through the IPM ACC disable feature. |
| • | The driver applied brake pressure. |
ECM Inhibits
The ECM inhibits the ACC System operation when any of the following conditions exists:
| • | The ACC inhibited signal from DSCC is present. |
| • | The vehicle speed is at or less than 40 km/h (25 mph). |
| • | The vehicle speed is greater than 193.1 km/h (120 mph). |
| • | Automatic braking failure--a GMLAN signal from EBCM to the ECM indicating an automatic braking failure |
| • | The ACC present signal from the IPM is false. |
| • | The driver applied brake pressure. |
| • | A cruise control switch failure is present. |
| • | The park brake switch signal from the IPM is active. |
| • | A Throttle Actuator Control (TAC) System failure is present. |
| • | The Traction Control System (TCS) is active. |
| • | The engine speed protection is active. |
| • | The vehicle speed protection is active. |
| • | The engine speed is too high or too low. |
| • | The automatic transmission is in first gear, Park, Neutral or Reverse. |
| • | The initial brake pedal travel signal from the BPP sensor is not present. |
| • | The system voltage is too low. |
Cruise Disengaged
The Adaptive Cruise Control (ACC) System disengages when any of the following occurs:
| • | The driver depresses the brake pedal. |
| • | The driver turns the ACC On/Off switch OFF. |
Pressing the brake pedal while the ACC is engaged will disengage the ACC System.
Other Adaptive Cruise Control (ACC) Features
Mechanical Alignment
When the radar is out of alignment, DTC C1002 is set by the distance sensing cruise control (DSCC) module. When DTC C1002 is set, it becomes necessary to mechanically align the radar using the special alignment tool. Refer to
DTC C1002 . For further information on how to aim and align the radar, refer to
Distance Sensing Cruise Control Aiming . An out of alignment condition may be as a result of tampering or damage to the DSCC module mounting structures or the 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 on how to properly mount and adjust the DSCC module. Performance of the adaptive cruise
control (ACC) System may be degraded after a DSCC module replacement. Normal vehicle driving will correct the performance of the ACC System.
