Speed Control (Service Information): Operation

The vehicle operator controls all speed control system features through the speed control switch stalk located to the left on the left side of the steering column. When a selection with the switch is made, it provides a hard wired resistor multiplexed analog input to the Body Control Module (BCM). The BCM is a gateway to the Controller Area Network (CAN) data bus not only reads the hard wired speed control switch and stop (brake) lamp switch inputs, but also relays these inputs to the Powertrain Control Module (PCM) over the CAN bus.

The PCM software continually monitors these inputs as well as electronic vehicle distance  message inputs from the Antilock Brake System (ABS) module and numerous hard wired inputs, then provides the appropriate electronic message and hard wired outputs to invoke the requested and programmed electronic speed control features.

The PCM also continually monitors all of the speed control system electrical circuits to determine the system readiness. If the PCM detects a monitored system fault, it sets and stores a Diagnostic Trouble Code (DTC). The PCM 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 Cruise indicator and the Malfunction Indicator Lamp (MIL) 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.