Cruise Control (Adaptive Cruise Control) Part 2

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:
- On/off switch
- Set/decrease switch
- Resume/increase switch

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 40 km/h (25 mph). The selected vehicle speed is displayed by the head-up display (HUD). 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. The current selected vehicle speed is displayed by the HUD. 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:
- No Activation
- Increase Gap
- Decrease Gap

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 distance sensing cruise control (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 On position and the vehicle speed is above 40 km/h (25 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 also 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 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 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. 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 module set speed display request is sent to the IPM via the GMLAN serial data circuit. The HUD displays the set speed when it receives a GMLAN serial data message from the IPM 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 module follow distance display request is sent to the IPM via the GMLAN serial data circuit. The HUD displays the follow distance when it receives a GMLAN serial data message from the IPM 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.

VEHICLE AHEAD INDICATOR
The vehicle ahead indicator is displayed in the HUD 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 HUD 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 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:
- 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 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 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 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 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 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 instrument panel module (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
- A HUD failure condition is present.
- The HUD is not turned ON.
- The brakes overheated signal from ABS
- A head-up display (HUD) failure condition is present
- 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 less than 32.2 km/h (20 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 ABS 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 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 ACC System may be degraded after a DSCC module replacement. Normal vehicle driving will correct the performance of the ACC System.