Part 2
Radio AmplifierThe 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 (Brake Pedal Position Sensor Calibration) and to Exterior Lighting Systems Description and Operation (Exterior Lighting Systems) 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:
* 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 (Procedures) 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 (Adjustments) , 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.