Part 3

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 (Adjustments) 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 on how to properly locate and mount the ACC module and the FLS.