Speed Control (Service Information): Operation: Adaptive

The vehicle operator controls all Adaptive Speed Control (ACC) system features through the speed control Steering Wheel Switch (SWS) pod on the face of the horizontal spoke of the steering wheel. When a push button of the SWS pod is depressed, it provides a Local Interface Network (LIN) switch input to the Steering Column Control Module (SCCM).

The SCCM reads the speed control switch input, then relays an electronic speed control switch status message to the Powertrain Control Module (PCM) and to the ACC module over the Controller Area Network (CAN) data bus. The PCM and ACC modules continually monitor these inputs as well as electronic wheel speed message inputs from the Antilock Brake System (ABS) module, electronic gear selector message inputs from the Transmission Control Module (TCM), video data from the Forward Facing Camera (FFC) and numerous hardwired inputs including the brake (stop) lamp sensor, then provides the appropriate electronic message and hardwired outputs to invoke the requested electronic speed control features.

Using the MODE push button of the speed control SWS pod on the face of the right horizontal spoke of the steering wheel, the vehicle operator can choose between ACC and conventional speed control modes of operation. As the name implies, when in the conventional speed control mode the speed control system is used and functions exactly like a conventional speed control system. When in the ACC mode, the vehicle operator can use the DISTANCE push button of the speed control SWS pod to select from one of three distance settings for the adaptive cruise system to maintain. These settings equate to the time in seconds separating the vehicle from a preceding vehicle. The FFC and the ACC module share a private bus allowing data fusion to occur within the ACC module. The ACC module then uses this information to send electronic message outputs to the ABS, the TCM and the PCM to maintain the selected separation distance. The available distance settings are:

• 1  - 1.0 second
• 2  - 1.5 seconds
• 3  - 2.0 seconds

If the PCM detects a fault on one of the following systems, it will disable the cruise control system and store an appropriate Diagnostic Trouble Code (DTC).

• Engine speed sensor
• Throttle Sensor or actuators (only for gasoline engines)
• Accelerator Pedal Potentiometer (APP) sensor
• Brake pedal position sensor
• Clutch switch rationality
• Engine load sensor (only for gasoline engines)
• Ignition coils (only for gasoline engines)
• Fuel injectors
• High pressure system components (only for diesel engines)
• Turbo sensors or actuators

The PCM and ACC modules continuously monitor all of the speed control system electrical circuits to determine the system readiness and accuracy. If the PCM or ACC module detects a monitored system fault, it sets and stores a DTC. The PCM and ACC components use On-Board Diagnostics (OBD) and can communicate with other electronic modules in the vehicle as well as with the diagnostic scan tool using the CAN data bus. This method of communication is used for control of the Malfunction Indicator Lamp (MIL) in the Instrument Panel Cluster (IPC) and for system diagnosis and testing through the 16-way Data Link Connector (DLC) located on the driver side lower edge of the instrument panel.

The hardwired inputs and outputs for the PCM and the ACC module may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the PCM, the ACC module or the electronic controls or communication between other modules and devices that provide features of the adaptive speed control system. The most reliable, efficient, and accurate means to diagnose the PCM, the ACC module or the electronic controls and communication related to speed control system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.