Instrument Cluster - Operation

OPERATION

The microprocessor-based IC hardware and software uses various inputs to control the gauges and indicators visible on the face of the cluster. The Vehicle Theft Alarm (VTA) lamp input is hard wired, the remaining 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 may also produce audible warnings for 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 switch output (run-start) circuit. This arrangement allows the IC to provide some features regardless of the ignition switch position, while other features will operate only with the ignition switch in the On or Start positions. The circuitry is grounded through a ground circuit of the instrument panel wire harness.

The IC also has a self-diagnostic test capability that tests each of the CAN bus message-controlled functions of the cluster. This test illuminates the appropriate indicators, positions the gauge needles at several predetermined calibration points across the gauge faces, and illuminates all segments of the Electronic Vehicle Information Center (EVIC). The EVIC will display the hardware/software version, and the CAN Vehicle Maintenance Monitor (VMM) used in the IC, Testing and Inspection.

LIQUID CRYSTAL DISPLAY

The LCD display unit is an integrated part, and soldered to the IC electronic circuit board. With the ignition switch in the Off or Accessory positions, the LCD display is activated when the driver door is opened (Rental Car mode), and deactivated when the driver door is closed. Otherwise, the display units are active when the ignition switch is in the ON or START positions, and inactive when the ignition switch is in the OFF or ACCESSORY positions.

The IC LCD display unit has several display capabilities. The LCD unit displays odometer, trip odometer, engine hours, gear selector indication (PRNDL) for models with an automatic transmission, several warning or reminder indications, and various diagnostics information when certain fault conditions exist. Steering wheel mounted switches are used to control some of the display modes of the LCD. Electronic Vehicle Information Center - Operation for more information.

CLUSTER ILLUMINATION

Instrument cluster illumination is supplied by several LED lamps controlled by the IC, and are illuminated at 100% intensity anytime the ignition switch is in the ON or RUN position. The illumination intensity of these lamps can be adjusted only when the vehicle park lamps are on by rotating the dimming control ring (down to dim, up to brighten). The IC monitors a CAN bus input from the Body Control Module (BCM) to determine illumination intensity.