Module, Adaptive Cruise Control (Acc): Operation

WARNING: This page is about a different car, the 2021 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.

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

The ACC module is also a Radio Detection And Ranging (RADAR) transceiver. The ACC module 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 module 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 module receives electronic speed control switch status message inputs from the microcontroller integral to the Steering Column Control Module (SCCM) over the Controller Area Network (CAN) data bus. The module also monitors electronic message inputs from the Powertrain Control Module (PCM), the Antilock Brake System (ABS) Module and the Transmission Control Module (TCM).

The ACC module 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 ABS to control and maintain the separation setting selected by the vehicle operator between the vehicle and any preceding vehicles. The ACC module also provides electronic message outputs to the Instrument Panel Cluster (IPC) and the Electronic Vehicle Information Center (EVIC) to invoke the Forward Collision Warning (FCW) features.

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

The ACC module microcontroller continuously monitors all of its internal electronics to determine the module readiness. If the ACC module detects a monitored module fault, it sets and stores a Diagnostic Trouble Code (DTC). The ACC module uses On-Board Diagnostics (OBD) and can communicate with other electronic modules in the vehicle as well as with the diagnostic scan tool over the CAN data bus. This method of communication is used for control of the indicators and indications provided to the vehicle operator through the Instrument Panel Cluster (IPC) and the EVIC. The ACC module is also Flash programmable, allowing the module software to be updated using a diagnostic scan tool.

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