Cruise Control Indicator - Operation

OPERATION

The cruise indicator indicates to the driver when the speed control system is on, regardless of whether or not the speed control is engaged. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Controller Area Network (CAN) data bus.

The cruise indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic only allows this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED is always off when the ignition switch is in any position except ON or START. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster turns the cruise indicator on for the following reasons:

- Cruise Indicator Lamp-On Message - Each time the cluster receives an electronic cruise indicator lamp-on message from the PCM indicating the speed control system is on, the cruise indicator is illuminated. The indicator remains illuminated until the cluster receives a lamp-off message from the PCM or until the ignition switch is turned to the OFF position, whichever occurs first.
- Self Test - Each time the cluster is put through the self test, the cruise indicator is turned on, then off again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.

The PCM continually monitors the speed control switches to determine the appropriate outputs to control the vehicle speed. The PCM then sends the proper lamp-on or lamp-off message to the instrument cluster, also known as the Cab Compartment Node (CCN). For further diagnosis of the cruise indicator or the instrument cluster circuitry that controls the LED, Component Tests and General Diagnostics.

A diagnostic scan tool is required for proper diagnosis of the speed control system, the PCM, the CCN, the CAN data bus or the electronic communication related to cruise indicator operation. Refer to the appropriate diagnostic information.