Adaptive Speed Control Sensor And Bracket - Operation

OPERATION

The microprocessor in the adaptive speed control sensor (also known as the Adaptive Cruise Control/ACC sensor or module, or as the radar sensor or module) contains the logic circuits and controls many of the features of the adaptive speed control system. The ACC sensor receives battery voltage on a fused ignition switch output (run) circuit and is grounded at all times through a hard wired remote ground point. These connections allow the ACC sensor to operate only when the ignition switch is in the ON position. Likewise, the ACC sensor sleeps whenever the ignition switch is in any position except ON.

The ACC sensor is also a Radio Detection And Ranging (RADAR) transceiver. The ACC sensor transmits electromagnetic signal bursts at an operating frequency of 77 gigahertz. Those signal bursts are scattered by any objects they strike within the 40 degree field of view of the transceiver, which changes the strength and frequency of the signal. The ACC sensor antenna receives and interprets the returned signals to detect any objects in the path of the vehicle as well as their speed and direction.

The ACC sensor receives electronic speed control switch status message inputs from the Steering Control Module (SCM) integral to the Steering Column Control Module (SCCM) over the Controller Area Network (CAN) data bus. The sensor also monitors electronic message inputs from the Powertrain Control Module (PCM), the Antilock Brake Module (ABM) (also known as the Controller Antilock Brake/CAB or the Electronic Stability Control/ESC module) and the Transmission Control Module (TCM).

The ACC sensor logic processes all of those inputs, then provides the appropriate electronic message outputs over the CAN data bus to the PCM, the TCM and the ABM to control and maintain the separation setting selected by the vehicle operator between the vehicle and any preceding vehicles. The ACC sensor also provides electronic message outputs to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) and the Electronic Vehicle Information Center (EVIC) to invoke the Forward Collision Warning (FCW) features.

Among other features, the sensor also contains an electronic ambient temperature sensor and a heating element. When appropriate ambient temperatures are sensed, the heating element is energized by the sensor control circuitry to keep the sensor lens or radar dome clear of ice and snow accumulations that might otherwise blind the sensor to proper reception of returned signals.

The ACC sensor microprocessor continuously monitors all of its internal electronics to determine the sensor readiness. If the ACC sensor detects a monitored sensor fault, it sets and stores a Diagnostic Trouble Code (DTC). The ACC sensor uses 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 indicators and indications provided to the vehicle operator through the EMIC and the EVIC. The ACC sensor is also Flash programmable, allowing the sensor software to be updated using a diagnostic scan tool.

The hard wired inputs for the ACC sensor 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 ACC sensor or the electronic controls or communication between other modules and devices that provide features of the adaptive speed control and FCW system features. The most reliable, efficient, and accurate means to diagnose the ACC sensor or the electronic controls and communication related to adaptive speed control or FCW system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.