Cruise Control System Cadillac XLR I

Fastener Tightening Specifications

Fastener Tightening Specifications

Cruise Control Schematic Icons

Cruise Control Schematic Icons Icon Icon Definition CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR Disabling and Enabling. Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Cruise Control Connector End Views

Adaptive Cruise Module (ACM)

Scheme 7

Cruise Control Connector End Views

Forward Looking Sensor (FLS)

Scheme 8

Cruise Control Connector End Views

Turn Signal/Multifunction Switch C1

Scheme 9

Cruise Control Connector End Views

Turn Signal/Multifunction Switch C2

Scheme 10

Cruise Control Connector End Views

Turn Signal/Multifunction Switch C3

Scheme 11

Cruise Control Connector End Views

Turn Signal/Multifunction Switch C4

Diagnostic Code Index

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Cruise Control

Begin the system diagnosis with the Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check will provide the following information

1. The identification of the control modules which command the system
2. The ability of the control modules to communicate through the serial data circuit
3. The identification of any stored diagnostic trouble codes (DTCs) and their status

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Scan Tool Output Controls

Adaptive Cruise Module (ACM) Scan Tool Output Controls

Adaptive Cruise Module (ACM) Module Setup (Japan Only)

Scan Tool Data List

The scan tool data lists contain all the distance sensing cruise control (DSCC) related parameters that are available on the scan tool for the adaptive cruise control (ACC) system. The parameters in the list are arranged in alphabetical order. The data list column indicates the location of the parameter within the scan tool menu selections.

Use the scan tool data lists as directed by a diagnostic table or in order to supplement the diagnostic procedures. Begin all of the diagnostic procedures with Diagnostic System Check - Vehicle .

Use the scan tool data lists only after the following is determined

1. There is no published DTC procedure nor published symptom procedure for the customer concern.
2. The DTC or symptom procedure indicated by the diagnostic system check does not resolve the customer concern.

The typical data values are obtained from a properly operating vehicle under the conditions specified in the first row of the scan tool data list table. Comparison of the parameter values from the suspect vehicle with the typical data values may reveal the source of the customer concern.

Body Control Module (BCM) Data List

DSCC Data List

Cruise Disengagement 1 - 4

Engine Control Module (ECM)

Scan Tool Data Definitions (Cruise Control)

The distance sensing cruise control (DSCC) module Scan Tool Data Definitions contains a brief description of all adaptive cruise control (ACC) system related parameters available on the scan tool.

Distance Sensing Cruise Control (DSCC) Module

The distance sensing cruise control module (DSCC) disengages cruise control for various reasons. The DSCC disengage reasons are available in the scan tool for display when the DSCC disengages cruise control. When a cruise control disengagement occurs, be sure to view both the DSCC data and engine control module (ECM) cruise disengagement data.

These Scan Tool Data Definitions contain a brief description of the cruise control disengage parameters available on the scan tool for display. One of the following conditions must be present in order for a disengagement parameter to be displayed

1. The cruise control system is active and disengagement is requested.
2. The engagement of the cruise control system is requested while a fault is present.

Engine Control Module (ECM)

The ECM disengages cruise control for various reasons. A list of all the reasons why the ECM disengages cruise control is available on the scan tool for display should a cruise control disengagement occur. The scan tool retains and only displays in the ECM Cruise Disengage History, the 8 most recent reasons for cruise control disengagement. It is important to note that in the ACC system, the DSCC also provides to the scan tool reasons for cruise control disengagement separate from the ECM list. Refer to Distance Sensing Cruise Control (DSCC) Data.

This Scan Tool Data Definition contains a brief description of the ECM cruise control disengage parameters available on the scan tool for display. One of the following conditions must be present in order for a disengagement parameter to be displayed

1. The cruise control system is active and disengagement is requested.
2. The engagement of the cruise control system is requested while a fault is present.

Circuit Description

The distance sensing cruise control module (DSCC) communicates with the radar forward looking sensor (FLS) via controller area network (CAN) serial data. When there is an internal fault in the FLS, this DTC will set in the DSCC.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B1020 Auxiliary Electronic Control Unit (ECU) Performance

This vehicle has DTCs which include DTC Symptoms. For more information on DTC symptoms, refer to Symptoms - Vehicle .

DTC B1020

Conditions for Running the DTC

The DSCC runs the program to detect a fault when power up is commanded.

Conditions for Setting the DTC

The module has detected a fault with the FLS while cruise is engaged or attempted to be engaged.

Action Taken When the DTC Sets

Adaptive cruise control (ACC) is inoperative.

Conditions for Clearing the DTC

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids

This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.

DTC B1020

The body control module (BCM) monitors the adaptive cruise control (ACC) gap adjustment switch signal circuit to determine the driver selected headway. The gap switch is a momentary contact switch that connects a series of resistors. Each switch state, inactive, up and down, corresponds to a specific resistance value. The BCM determines the switch selection by the voltage drop across the resistor. The BCM sets DTC B3623 when it detects a stuck gap up/down switch.

This diagnostic procedure supports the following DTC

DTC B3623 Steering Wheel Controls Adaptive Cruise Control (ACC) Gap Up/Down Signal Circuit.

DTC B3623

Ignition is in RUN.

Gap adjustment switch signal circuit remains in the same state for 1 minute

Gap +/- switch remains in the last selected position

Conditions for Clearing the MIL/DTC

1. The DTC becomes history when the fault is no longer present.
2. A History DTC clears after 100 malfunction free ignition cycles.
3. The BCM module receives a clear code command from the scan tool.

Refer to Testing for Intermittent Conditions and Poor Connections .

DTC B3623

The body control module (BCM) monitors the cruise control set/coast and resume/accel switch signal circuit in order to detect when the driver has requested a cruise control switch function. The BCM determines which cruise control switch function is being requested based on a predetermined voltage signal from the cruise control switch.

This diagnostic procedure supports the following DTC

DTC B3794 Cruise Control Function Request Circuit

DTC B3794

1. The cruise control On/Off switch is ON.
2. The engine is ON.

1. The BCM detects an invalid voltage signal on the cruise control set/coast and resume/accel switch signal circuit.
2. The above condition is present for 1 second.

1. The malfunction indicator lamp (MIL) will not illuminate.
2. The BCM stores the DTC information into memory when the diagnostic runs and fails.
3. The Adaptive Cruise Control (ACC) System is disabled.
4. Cruise Not Ready indicator displays in the driver information center (DIC).

1. The DTC becomes history when the fault is no longer present.
2. A History DTC clears after 100 malfunction free ignition cycles.
3. The BCM module receives a clear code command from the scan tool.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

DTC B3794

Circuit/System Description

The distance sensing cruise control module (DSCC) monitors the ignition 1 voltage circuit to determine if the voltage is within the normal operating range. When the DSCC detects that the ignition 1 voltage is below 9.2 V or above 16 V, the DTC C0800 sets.

C0800 03 and 07

1. Ignition is in RUN.
2. Vehicle moving at a speed greater than 40.2 km/h (25 mph).

C0800 03

1. The DSCC detects that the ignition 1 voltage is less than 9.2 volts.
2. The above condition is present for 7 seconds.

C0800 07

1. The DSCC detects that the ignition 1 voltage is greater than 16 volts.
2. The above condition is present for 7 seconds.

C0800 03 and 07

The following actions occur

1. Loss of adaptive cruise function.
2. Cruise Not Ready indicator illuminates in the DIC.

1. The DTC becomes history when the fault is no longer present.
2. A History DTC clears after 100 malfunction free ignition cycles.
3. The DSCC receives a clear code command from the scan tool.

Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.

Reference Information

Schematic Reference

Cruise Control Schematics

Connector End View Reference

Master Electrical Component List

Electrical Information Reference

1. «Circuit Testing»(/cadillac/xlr/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__circuit-testing)
2. «Connector Repairs»(/cadillac/xlr/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/xlr/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/xlr/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__wiring-repairs)

Scan Tool Reference

Scan Tool Data List

Circuit/System Verification

1. Ignition ON, verify that DTC P0562, P0563 in the ECM and/or B1325 in the BCM are not current. If one of those DTCs is found as a current DTC, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/xlr/i-2003-2009/remont/oem-general-information/#vehicle-dtc-information__diagnostic-trouble-code-dtc-list) .
2. Verify that DTC C0800 is current in the scan tool. If the DTC is not current, refer to «Charging System Test»(/cadillac/xlr/i-2003-2009/remont/charging-system/#battery-charging-system-and-starting-system__charging-system-test) . If the DTC is current, go to Circuit/System Testing.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the distance sensing cruise control module (DSCC).
2. Ignition ON, test for greater than 9.2 volts between the ignition 1 voltage circuit terminal 14 and ground. If less than the specified value, test the voltage circuit for an open/high resistance.
3. Ignition ON, test for greater than 9.2 volts between the ignition 1 voltage circuit terminal 14 and the ground circuit terminal 12. If less than the specified value, test the ground circuit for an open/high resistance.
4. Engine ON, test for less than 16 volts between the ignition 1 voltage circuit terminal 14 and ground. If greater than the specified value, test the voltage circuit for a short to voltage. If the circuit tests normal, refer to «Charging System Test»(/cadillac/xlr/i-2003-2009/remont/charging-system/#battery-charging-system-and-starting-system__charging-system-test) .
5. If all circuits test normal, test or replace the DSCC.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for DSCC replacement, setup, and programming.

The forward looking sensor (FLS) has the exclusive function of detecting, tracking and classifying targets within its specified field of view. The FLS has the ability to detect and react to objects of interest in its detection zone and is critical to the proper operation of the Adaptive Cruise Control (ACC) System. When the distance sensing cruise control module (DSCC) detects that the FLS is out of alignment, DTC C1002 sets.

This diagnostic procedure supports the following DTC

DTC C1002 Distance Sensing Cruise Control Module Range/Performance

The ignition is ON.

1. 2.5 degrees of skew or error of the FLS
2. Vehicle has been driven for some time

1. Loss of ACC function
2. Service Radar Cruise indicator illuminates in the driver information center (DIC).

1. The DTC becomes history when the conditions for setting the DTC are no longer present.
2. The history DTC clears after 100 malfunction-free warm-up cycles.
3. The DSCC receives a clear code command from the scan tool.

1. The FLS radar is equipped with an internal automatic alignment feature. The FLS radar alignment is continuously assessed and adjusted as necessary during ACC vehicle operation by the DSCC. Refer to «Cruise Control Description and Operation (Adaptive Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system) or «Cruise Control Description and Operation (Conventional Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__cruise-control-description-and-operation-conventional) for more information on the FLS radar automatic alignment feature.
2. When automatic alignment is not achieved by the FLS radar and an out of alignment diagnostic is reported by the DSCC, it is necessary to mechanically align the FLS radar using the FLS alignment tool. Refer to «Distance Sensing Cruise Control Aiming»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__distance-sensing-cruise-control-aiming) to properly align the FLS radar. The typical DSCC alignment value is 0°+/-2°.
3. An FLS radar out of alignment condition may be as a result of tampering with the DSCC mounting structures/brackets or the adjuster settings. An out of alignment condition may be a result of damage to the front section of the ACC vehicle or the DSCC. Refer to «Distance Sensing Cruise Control Aiming»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__distance-sensing-cruise-control-aiming) and «Distance Sensing Cruise Control Bracket Replacement»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__distance-sensing-cruise-control-bracket-replacement) to properly adjust or replace the DSCC or the DSCC brackets.
4. An out of alignment condition may be because the FLS radar has not achieved a complete internal automatic alignment. For the FLS radar to achieve a complete automatic alignment and process the road environment correctly, the ACC vehicle needs to be driven on a road with stationary objects (mail boxes, road signs, trees, ramps 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 the vehicle is travelling. The more stationary objects encountered, the quicker the FLS radar will achieve automatic alignment. When the DSCC is replaced with a new module, it is necessary to drive the vehicle with the new module until the automatic alignment is complete. Performance of the ACC system may be degraded after DSCC replacement. Normal vehicle driving will correct the performance of the ACC system. Refer to «Cruise Control Description and Operation (Adaptive Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system) or «Cruise Control Description and Operation (Conventional Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__cruise-control-description-and-operation-conventional) .

When a cruise control function switch is activated, the body control module (BCM) detects a predetermined voltage signal. The BCM sends a GMLAN serial data message to the engine control module (ECM) indicating the function that has been requested.

This diagnostic procedure supports the following DTC

DTC P0575 Cruise Control Switch Signal Circuit

The engine is ON.

1. The ECM receives an invalid cruise control switch status GMLAN serial data message from the BCM.
2. This diagnostic runs continuously.

1. The Cruise Control System is disabled.
2. The ECM stores the DTC information into memory when the diagnostic runs and fails.
3. The malfunction indicator lamp (MIL) will not illuminate.
4. The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
5. All cruise control function switches are set to OFF.

1. A last test failed, or the current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic.
3. Use the scan tool in order to clear the DTC.

1. This DTC may be stored as a history DTC without affecting the operation of the BCM. If stored only as a history DTC and not retrieved as a current DTC, do not replace the BCM.
2. If this DTC is retrieved as both a current and history DTC, replace the BCM.

DTC P0575

The body control module (BCM) sends brake signals via the GMLAN serial data circuit to the transmission control module (TCM) and to the engine control module (ECM) indicating the status of the stop lamps.

This diagnostic procedure supports the following DTC

DTC P0703 Brake Switch Circuit 2

The engine is ON.

1. The TCM or the ECM detects a missing or invalid brake signal from the BCM.
2. This diagnostic runs continuously.

1. The malfunction indicator lamp (MIL) will not illuminate.
2. The autograde braking is inhibited.
3. The Cruise Control System is disabled.
4. The TCM and the ECM stores the DTC information into memory when the diagnostic runs and fails.
5. The TCM and the ECM records the operating conditions at the time the diagnostic fails. The TCM and the ECM stores this information in the Failure Records.

1. The DTC becomes history when the fault is no longer present.
2. A History DTC clears after 100 malfunction free ignition cycles.
3. Use the scan tool in order to clear the DTC.

1. If a BCM has been replaced, the BPP sensor must be calibrated. Refer to «Brake Pedal Position Sensor Calibration»(/cadillac/xlr/i-2003-2009/remont/exterior-lights/#lighting-systems-introduction-2-of-2) .
2. This DTC may be stored as a history DTC without affecting the operation of the BCM. If stored only as a history DTC and not retrieved as a current DTC, do not replace the BCM.
3. If this DTC is retrieved as both a current and a history DTC, replace the BCM.
4. For an intermittent condition, refer to «Testing for Intermittent Conditions and Poor Connections»(/cadillac/xlr/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__testing-for-intermittent-conditions-and-poor) .

Test Description

The numbers below refer to the step numbers located in the diagnostic table.

1. 2: This step is performed in order to confirm that DTC P0703 is current within the TCM or the ECM.
2. 3: This step is performed in order to correct a BPP sensor that must be calibrated, possibly due to a BCM replacement or for a BPP sensor that is out of adjustment.

DTC P0703

Symptoms - Cruise Control

1. Before using the symptom diagnostic table, perform the «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/xlr/i-2003-2009/remont/oem-general-information/#vehicle-dtc-information__diagnostic-trouble-code-dtc-list) in order to verify the following conditions: There are no DTCs set. The module can communicate via the GM LAN.
2. Review the system operation in order to understand the system functions. Refer to «Cruise Control Description and Operation (Adaptive Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system) or «Cruise Control Description and Operation (Conventional Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__cruise-control-description-and-operation-conventional) .

Visual/Physical Inspection

1. Inspect for aftermarket devices which can affect the operation of the cruise control system. Refer to «Checking Aftermarket Accessories»(/cadillac/xlr/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__checking-aftermarket-accessories) .
2. Inspect the accessible system components or the visible system components for obvious damage or for obvious conditions which can cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

1. «Cruise Control Inoperative/Malfunctioning»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system) .
2. «Cruise Control Gap Up/Down Switch Malfunction»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__cruise-control-gap-updown-switch-malfunction) .

Cruise Control Gap Up/Down Switch Malfunction

Cruise Control Gap Up/Down Switch Malfunction

In order to avoid a misdiagnosis, inspect for proper operation of the brake lamps. Refer to Exterior Lighting Systems Description and Operation .

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

Electromagnetic Interference on the vehicle speed sensor signal circuit may cause erratic cruise control operation.

Conditions for Enabling Cruise Control

1. The CRUISE NOT READY message is not illuminated in the DIC.
2. The vehicle speed is greater than 40 km/h (25 mph).
3. The vehicle is not in PARK, REVERSE, NEUTRAL, or 1st gear.
4. The system voltage is within 9.2 volts and 16 volts.
5. The park brake is released.
6. The forward looking sensor (FLS) is radiating and the adaptive cruise module (ACM) has identified acceptable stationary or moving objects.

The number below refers to the step number on the diagnostic table.

1. 5: This step tests the cruise control switch supply voltage circuit for an open, for a short to ground, or for a high resistance.

Cruise Control Inoperative/Malfunctioning

Scheme 12

Distance Sensing Cruise Control Module Replacement

Distance Sensing Cruise Control Bracket Replacement

Distance Sensing Cruise Control Bracket Replacement

Distance Sensing Cruise Control Aiming

1. Place a bubble level against the front of the radar. Adjust the vertical control until the radar is level.
2. For horizontal adjustment, measure the back of the horizontal adjuster. Adjust the horizontal until 6 mm (0.25 in) of the adjuster is protruding out behind the radar. This method should work assuming that the bracket and frame have not been damaged in a collision.
3. Use a scan tool to perform a Factory Reset of the adaptive cruise module (ACM). Ensure that the Auto Alignment Learn Status parameter indicates Not Aligned. This allows the forward looking sensor (FLS) to automatically align itself during vehicle driving.
4. Drive the vehicle at speeds of at least 56 kph (35 mph), so that the automatic alignment process can operate. The process requires the radar to observe stationary targets along the edge of the road (i.e. mail boxes, parked cars, poles, signs, etc.). Do not follow other vehicles too closely, since this obscures the view for the radar.
5. Use a scan tool to monitor the Auto Alignment Learn Status parameter. Continue driving until the Auto Alignment Learn Status parameter indicates Aligned. Typically, it will require less than 10 miles of driving. If not proceed to step #4. If the resulting Alignment Error is within -1.5 and 1.5 degrees, the alignment is within specification. Otherwise, proceed to step #6.
6. Adjust the horizontal adjuster according to the Alignment Error chart provided below. Then, repeat steps 3, 4, and 5.

Adaptive Cruise Control Horizontal Adjustment Table

Removal Procedure

1. Open the hood.
2. Remove the left front section (1) of the air cleaner assembly.
3. Disconnect the electrical connector from the vehicle distance module sensor assembly (2).
4. Remove the sensor assembly from the fascia (1).
5. Remove the three bolts (1) attaching the sensor assembly to the bracket.

Installation Procedure

1. Position the sensor assembly to the bracket.
2. Hand tighten the three bolts that attach the sensor assembly to the bracket. Tighten: Tighten the bolt to 10 N.m (7 lb ft).
3. Connect the electrical connector to the sensor assembly (2).
4. Install the sensor assembly cover to the fascia (1).
5. Install the left front section (1) of the air cleaner assembly.
6. Close the hood.
7. With the scan tool, change the Automatic Alignment Learn Status Parameter in the DSCC module scan tool data list to Not Aligned after replacing the sensor assembly. This allows the new sensor assembly to automatically align to the vehicle during normal customer driving. Refer to «Scan Tool Data List»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__scan-tool-data-list) and «Cruise Control Description and Operation (Adaptive Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system) or «Cruise Control Description and Operation (Conventional Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__cruise-control-description-and-operation-conventional) .
8. Performance of the ACC system may be degraded after sensor assembly replacement. Normal customer driving will correct the performance of the ACC system. Refer to «Cruise Control Description and Operation (Adaptive Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system) or «Cruise Control Description and Operation (Conventional Cruise)»(/cadillac/xlr/i-2003-2009/remont/cruise-control-systems/#cruise-control-system__cruise-control-description-and-operation-conventional) .
9. Refer to «Control Module References»(/cadillac/xlr/i-2003-2009/remont/communication-devices/#computerintegrating-systems__control-module-references) for programming and setup information.

Distance Sensing Cruise Control Maintenance

1. Remove the distance sensing cruise control (DSCC) module cover from the fascia (1).
2. Clean the surfaces of the inner and outer DSCC module cover with a 50/50 mixture of isopropyl alcohol and water by volume on a dampened lint free cloth.
3. With the same solution, clean the outer surface of the DSCC module (1).
4. Install the DSCC module cover to the fascia (1).

Adaptive Cruise Control (ACC)

The Adaptive Cruise Control (ACC) System 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 module (DSCC) 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 vehicles speed and acceleration along with the ACC vehicle speed and acceleration and the distance between the 2 vehicles are factors used by the DSCC 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 General Motors local area network (GMLAN) and the class 2 serial data circuit. The body control module (BCM) provides a translating gateway function between the class 2 and the GMLAN data links. The GMLAN utilizes the controller area network (CAN) communications protocol. The following is a functional description of the distance sensing cruise control module (DSCC) and the other associated components

Distance Sensing Cruise Control Module (DSCC)

The distance sensing cruise control module (DSCC) communicates with the forward looking sensor (FLS) via controller area network (CAN) serial data. The DSCC utilizes the FLS to identify and classify objects in the road environment. The FLS scans the road environment to detect targets within its specified field of view. The DSCC then makes throttle and/or brake commands to the engine control module (ECM) and electronic brake control module (EBCM) via GMLAN serial data circuit to control vehicle acceleration/deceleration based on data from the FLS 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 to determine the predicted path of the adaptive cruise control (ACC) vehicle. The main power feed for the DSCC 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 has to be 9.2 volts or more to be considered active. When the ignition 1 signal is not active, all ACC functions are disabled. The following is a list of the DSCC functions

1. The FLS 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 FLS functions. When an object is detected, the DSCC calculates the object range, range rate, acceleration and azimuth angle parameters.
2. The DSCC 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 FLS, 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 2 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.
3. The DSCC determines the Follow Speed limit for throttle control by the ECM.
4. The DSCC arbitrates the ACC system brake and throttle control between the EBCM and the ECM.
5. The DSCC requests brake light activation during automatic braking.
6. The DSCC provides operational feedback to the vehicle driver. The DSCC sends signals for telltales and messages to be displayed on the head-up display (HUD) or driver information center (DIC) via the body control module (BCM). The DSCC will provide audible feedback to the driver via the BCM and the radio amplifier as well.

Body Control Module (BCM)

The following are the ACC system functions provided by the BCM

1. The BCM provides a translating gateway between the class 2 serial data circuit and the high speed GMLAN serial data circuit.
2. The BCM reads all cruise control switches and the gap switch. The DSCC monitors a variety of user operated switches from the BCM switch status information sent via the GMLAN serial data circuit.
3. The BCM illuminates the brake light based on a GMLAN message from the DSCC during automatic braking.
4. The BCM 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.
5. The BCM serves as a gateway to the display system's (HUD, IPC, DIC and Amplifier) visual and audible warnings. The BCM will generate visual and audible warning class 2 messages based on high speed GMLAN signals from the DSCC.

The following are the ACC system functions performed by the ECM

1. 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.
2. The ECM processes the cruise control switch requests received via the GMLAN serial data circuit from the BCM. Engaging and disengaging the ACC system are functions performed by the ECM.
3. 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.
4. The ECM allows automatic braking without disengaging the ACC.

Electronic Brake Control Module (EBCM)

The following are the ACC system functions performed by the EBCM

1. The EBCM provides automatic braking for the ACC system. The DSCC will request vehicle deceleration via high speed GMLAN serial data circuit.
2. 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 BCM.
3. The EBCM releases vehicle automatic braking when there is a throttle override by the driver pressing the accelerator.
4. 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.
5. The EBCM calculates yaw rate and provides the yaw rate data to the DSCC for vehicle path predictions.

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 the ABS braking activity, extend brake pad life and reduce brake overheating.

Driver Information Center (DIC)

The DIC is a part of the instrument panel cluster (IPC) and displays the ACC system warning messages. The DSCC requests messages to be displayed on the DIC by sending a GMLAN request to the BCM. The BCM sends a class 2 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

1. Service Radar Cruise
2. Cruise Not Ready
3. Clean Radar

Head-Up Display (HUD)

The head-up display (HUD) displays ACC system telltales and status information. The DSCC sends a message to the BCM via the GMLAN serial data circuit requesting the display of a HUD telltale. The HUD displays the telltale when it receives a class 2 message from the BCM demanding illumination of the telltale. Feedback to a driver action takes precedence over other status information sent to the HUD by the BCM. The HUD is enabled in power mode RUN. The driver may have to adjust the position of the HUD or the intensity of the display to see the information being displayed. The ACC system will not operate if the HUD fails. The HUD displays the following telltales and ACC status indicators

1. Cruise Speed Limited Message
2. Cruise Engaged Telltale
3. Vehicle Ahead Telltale
4. Tight Curve Message
5. Follow Distance Display
6. Set Speed Display
7. Driver Alert Telltale
8. Vehicle Speed Display

Radio Amplifier

The amplifier receives audible warning commands via a class 2 message from the BCM. 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 brake pedal position (BPP) sensor helps the BCM 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 BCM. When the brake is applied, a signal is applied from the BPP sensor through the BPP sensor signal circuit to the BCM. The BCM utilizes this signal in deciding when to command the activation of the stop lamps. The BCM 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 BCM. When the BCM 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 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. The DSCC 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

1. On/Off Switch
2. Set/Decrease Switch
3. 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 body control module (BCM) 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 BCM is then sent to the engine control module (ECM) as a General Motor local area network (GMLAN) serial data circuit message. The ECM on receiving the message provides the cruise control function requested by the BCM. The ECM is responsible for recognizing and responding to cruise control switch requests sent by the BCM. The cruise control function switches are used by the ECM to communicate to the distance sensing cruise control module (DSCC) the driver selected vehicle speed. The driver selected vehicle speed is communicated through GMLAN serial data circuit to the DSCC and the BCM. The ACC system engages and adjusts vehicle speeds based on the activation of the following cruise control function switches

On/Off Switch

The BCM monitors the On/Off switch status and makes a determination that the On/Off switch is activated based on a predetermined voltage value at the cruise control switch signal circuit. The On/Off switch state is then relayed to the ECM via the GMLAN serial data circuit. The ECM will recognize and communicate the On/Off switch input to the DSCC. When the On/Off switch is turned ON, it will cause the ACC system to enter either STANDBY ENABLED or STANDBY DISABLED state. The STANDBY ENABLED state indicates that every condition required for the ACC system to function have been met but the ACC is not yet engaged. When in the STANDBY DISABLED state, all conditions necessary for the ACC to function has not been met. When the On/Off switch is turned OFF, ACC will enter the DISABLED state. ACC will not be active in the DISABLED state. When automatic braking is active and the ACC On/Off switch is turned OFF, ACC will delay entering the DISABLED state.

Set/Decrease Switch

The ACC system is engaged when the vehicle driver presses and releases the set/decrease switch. The engaged state of the ACC system can only be entered when the On/Off switch is turned ON. When the set/decrease switch is pressed, the driver selected speed is set to the current vehicle speed by the ECM. The vehicle speed must be above 40 km/h (25 mph). The current driver selected speed is displayed by the head-up display (HUD). While in the engaged state, the driver selected vehicle speed and following distance can be adjusted. Pressing the set/decrease switch when the ACC system is engaged allows the driver to decrease the driver selected vehicle speed. Pressing and holding the set/decrease switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating ACC. The Tap-Down function occurs by momentarily pressing and releasing the set/decrease switch when ACC is engaged. With the Tap-Down function, the driver selected speed is decreased by 1 km/h (1 mph) each time the set/decrease switch is pressed.

The Resume/Increase Switch

When in the resume/increase state, ACC is active and the previously set driver selected speed has not been cleared. The resume/increase switch is used to increase the driver selected speed when ACC is active. The extent to which the driver selected 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 driver selected speed can be achieved. If there is no preceding vehicle in front limiting the ACC vehicle acceleration, the current vehicle speed attained is the new driver selected speed. The current driver selected 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 result in the Tap-Up function. With the Tap-Up function, the driver selected speed is increased in increments of 1 km/h (1 mph).

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 up/down switch is hard-wired to the body control module (BCM) and voltage is provided to the switch from the BCM via the gap up/down ignition 1 voltage circuit. Based on voltage variations, the BCM 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 module (DSCC). The gap up/down switch is a 3-position momentary switch - Center, Gap Up and Gap Down - with the following valid signal values

1. No Activation
2. Increase Gap
3. 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 BCM will default to increasing the gap value.

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

1. The DSCC is requesting maximum automatic braking.
2. The DSCC automatic braking request is not sufficient to safely stop the vehicle in certain road conditions.
3. Cruise disengagement not initiated by driver or any driver action.
4. The vehicle speed is below 32 km/h (20 mph).
5. 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

1. On/Off
2. Set/Decrease
3. 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.

DSCC Inhibits

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

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

ECM Inhibits

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

1. ACC inhibited signal from DSCC is present.
2. Vehicle speed drops below 32.2 km/h (20 mph).
3. Vehicle speed is above 193.1 km/h (120 mph).
4. Automatic braking failure - GMLAN signal from ABS to ECM indicating automatic braking failure
5. ACC present signal from BCM is false.
6. Driver applied brake pressure.
7. Cruise Control switch failure
8. Park brake switch signal from BCM is active.
9. Electronic throttle control (ETC) failure
10. Traction control is active.
11. ABS is active.
12. Engine overspeed protection is active.
13. Vehicle overspeed protection is active.
14. Engine speed is too high or too low.
15. Automatic transmission is in First gear, Park, Neutral or Reverse.
16. Initial brake pedal travel signal from BPPS not present
17. System voltage is low.

Cruise Disengaged

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

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

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

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.

Cruise Control Description and Operation (Conventional Cruise)

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

1. The accelerator pedal
2. The brake pedal position (BPP) sensor
3. The body control module (BCM)
4. The cruise control on/off switch
5. The engine control module (ECM)
6. The + RES switch
7. The - SET switch
8. The throttle actuator control (TAC) motor
9. The transmission control module (TCM)
10. 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

1. On/off
2. + RES
3. SET

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 review of the TAC system, refer to Throttle Actuator Control (TAC) System Description for the 4.4L engine.

Ignition voltage is supplied to the cruise control switch from the 2-ampere STRG COL SW fuse located in the integrated BCM fuse block. The cruise control function 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 any cruise control function switch being activated. When the normally open cruise control on/off switch is turned ON, the switch closes and the BCM detects a predetermined voltage signal on the cruise control set/coast and resume/accel switch signal circuit. The BCM sends a GMLAN serial data message to the ECM indicating that the on/off switch is active. Similarly, when the + RES switch or the - SET switch are pressed, the BCM detects the predetermined voltage signal on the cruise control set/coast and resume/accel switch signal circuit. To engage the Cruise Control System, ensure that the vehicle speed is above 40.2 km/h (25 mph), turn the cruise 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 BCM. The BCM then sends a class 2 serial data message to the head-up display (HUD) in order to illuminate the Cruise Speed SET XXX message.

The - SET switch or 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 the - SET switch will allow the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the - SET 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 pressing the + RES switch after the Cruise Control System has been disengaged by pressing the brake pedal, will recall the previous set vehicle speed that is recorded in the ECM.

Cruise Control Disengaged

The engine control module (ECM) disengages the cruise control operation based on the signals from the following switches

1. The brake pedal position (BPP) sensor
2. The cruise control On/Off switch

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 body control module (BCM) monitors the BPP sensor via the brake pedal position sensor signal circuit. The BCM sends a GMLAN serial data message to the ECM and to the transmission control module (TCM) indicating the position of the brake pedal. For further information on the BPP sensor, refer to Exterior Lighting Systems Description and Operation or to Brake Pedal Position Sensor Calibration .

The Cruise Control System will also disengage when the cruise control On/Off switch is switched OFF or when the ECM detects that a driver override function has been active for approximately 60 seconds.

When the Cruise Control System has been disengaged, the ECM sends a GMLAN serial message to the BCM. The BCM then sends a class 2 serial data message to the HUD in order to turn OFF the Cruise Speed SET XXX 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

1. A Cruise Control System DTC has been set.
2. The vehicle speed is less than 40.2 km/h (25 mph).
3. The vehicle speed is too high.
4. The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear.
5. The engine RPM is too low.
6. The engine RPM is too high.
7. The system voltage is not between 9-16 volts.
8. The Antilock Brake System/Traction Control System is active for more than 2 seconds.

See also:
• Diagnostic System Check - Vehicle
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Control Module References
• Master Electrical Component List
• Circuit Testing
• Wiring Repairs
• Steering Wheel Control Switch Assembly Replacement
• Diagnostic Trouble Code (DTC) List - Vehicle
• Charging System Test
• Diagnostic Repair Verification
• Computer/Integrating Systems Connector End Views
• Brake Pedal Position Sensor Calibration
• Checking Aftermarket Accessories
• Engine Control Module Connector End Views
• Rear Window Panel Trim Replacement
• Fastener Notice
• ABS Description and Operation
• Throttle Actuator Control (TAC) System Description
• DTC B1020
• Scan Tool Data List
• Cruise Control Description and Operation (Conventional Cruise)
• Distance Sensing Cruise Control Aiming
• Distance Sensing Cruise Control Bracket Replacement
• Cruise Control Gap Up/Down Switch Malfunction
• Distance Sensing Cruise Control Maintenance