Instrument Cluster - Operation

OPERATION

The Instrument Cluster (IC) (also known as the Instrument Panel Cluster/IPC) is designed to allow the vehicle operator to monitor the conditions of many of the vehicle components and operating systems. The gauges and indicators in the IC provide valuable information about the various standard and optional powertrains, fuel and emissions systems, cooling systems, lighting systems, safety systems and many other convenience items. The IC is installed in the instrument panel so that all of these monitors can be easily viewed by the vehicle operator when driving, while still allowing relative ease of access for service.

The microcontroller-based IC hardware and software uses various inputs to control the gauges and indicators visible on the face of the IC. These inputs are in the form of electronic messages that are transmitted by other electronic modules over the Controller Area Network (CAN) data bus. Communication - Operation.

The IC microcontroller smooths the input data using algorithms to provide gauge readings that are accurate, stable and responsive to operating conditions. These algorithms are designed to provide gauge readings during normal operation that are consistent with customer expectations. However, when abnormal conditions such as high coolant temperature occur, the algorithm can drive the gauge pointer to an extreme position and the microcontroller can sound an audible alert through the on-board audible tone transducer to provide distinct visual and audible indications of a problem to the vehicle operator. The IC may also produce audible warnings on behalf of other electronic modules in the vehicle based upon electronic tone request messages received over the CAN data bus. Each audible warning is intended to provide the vehicle operator with an audible alert to supplement a visual indication.

The IC circuitry operates on battery current received through a non-switched fused B(+) circuit, and on battery current received through a fused ignition output (run) fuse on a fused ignition output (run) circuit. This arrangement allows the IC to provide some features regardless of the status of the ignition switch, while other features will operate only when the status of the ignition switch is ON. The IC circuitry has a path to ground at all times through a takeout of the instrument panel wire harness that is secured to the instrument panel support structure.

The IC also has a self-diagnostic test capability which will test each of the CAN bus message-controlled functions of the IC by lighting the appropriate indicators, positioning the gauge needles at several predetermined calibration points across the gauge faces and illuminating all segments of the electronic display unit. The electronic display unit will also display the software version used in the IC. Testing and Inspection.

CLUSTER ILLUMINATION

The IC has several Light-Emitting Diode (LED) units that serve as general illumination lighting for the IC. These LED units are illuminated whenever the exterior lighting is turned ON. The illumination intensity of these LED units is adjusted when the panel dimmer thumbwheel on the dimmer module is rotated (down to dim, up to brighten) to one of six available minor detent positions.

The Body Control Module (BCM) monitors a hard wired resistor multiplexed input from the dimmer module on a dimmer input circuit. In response to that input, the BCM sends an electronic dimming level message to the IC over the CAN data bus. The electronic circuitry of the IC then converts a fused 12-volt input it receives into a 12-volt Pulse Width Modulated (PWM) output. The IC uses this PWM output to control the illumination intensity of the general illumination of the IC and provides a hard wired PWM output to other components on the instrument panel and within the vehicle interior to control and synchronize their illumination intensity.

In addition, the thumbwheel on the dimmer module has a Parade Mode position to provide a parade or funeral mode. The BCM monitors the request for this mode from the dimmer module, then transmits an electronic dimming level message to illuminate all electronic display units in the vehicle at full (daytime) intensity for easier visibility when driving in daylight with the exterior lighting turned ON.

The hard wired headlamp switch and panel lamps dimmer inputs to and outputs from the BCM may be diagnosed using conventional diagnostic methods. However, proper testing of the PWM processing of the IC and the electronic dimming level messages sent by the BCM over the CAN data bus requires the use of a diagnostic scan tool. .

ELECTRONIC DISPLAY UNIT

When the status of the ignition switch is OFF, the electronic display unit is inactive and the total odometer information is displayed only when the driver side front door is open and is deactivated when the driver side front door is closed. Otherwise, the display unit is only active and the total odometer information is only displayed when the status of the ignition switch is ON/RUN or Accessory (ACC), and is inactive when the status of the ignition switch is OFF.

- Odometer/Trip Odometer Display Toggling - Momentarily actuating the appropriate push button within the odometer switch pod or the EVIC switch pod (depending on how equipped) with the electronic display unit active, will toggle the display between the total odometer and trip odometer information.

- Trip Odometer Reset - Actuating the appropriate push button within the odometer switch pod or the EVIC switch pod (depending on how equipped) for longer than about two seconds while the status of the ignition switch is ON will reset the active trip odometer (A or B) to 0.0 kilometers (miles). Only the trip odometer information being currently displayed (active) will be reset.

- Communication Error - If the IC fails to receive an electronic distance message during normal operation, it will hold and display the last data received until the status of the ignition switch is OFF. If the IC does not receive a distance message within one second after the ignition switch status transitions to ON, it will display the last distance value stored in IC memory. If the IC is unable to display distance information due to an error internal to the IC, the electronic display unit will display Error.

- Self Test - Each time the IC is put through the self diagnostics test, the electronic display unit will illuminate all of its segments simultaneously to confirm the functionality of the display and the IC control circuitry.