Instrument Cluster - Operation

OPERATION

The Instrument Cluster (IC) 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 the operator of the vehicle can view all of these monitors easily, yet still allow relative ease of access for service.

The microprocessor-based IC hardware and software uses various inputs to control the gauges and indicators visible on the face of the cluster. Some of these inputs are hard wired, but most are in the form of electronic messages that are transmitted by other electronic modules over the Controller Area Network (CAN) data bus and the Local Interconnect Network (LIN) data bus. Communication - Operation.

The IC microprocessor 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 exist such as high coolant temperature, the algorithm can drive the gauge pointer to an extreme position and the microprocessor can sound to provide distinct visual and audible indications of a problem to the vehicle operator. 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 fused B(+) fuse on a non-switched fused B(+) circuit, and on battery current received through a fused ignition switch output (run-start) fuse on 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 within the Thin Film Transistor (LCD) display unit and. Testing and Inspection.

The IC collects data and provides control signals for the following electrical equipment via the CAN data bus:

- Gauges
- Variable-intensity cluster lighting and illumination of instrument panel mounted equipment
- Vehicle Theft Alarm and Sentry Key Theft Deterrent System
- Power door lock system controls (automatic locking, and Remote Keyless Entry locking and unlocking)
- Steering wheel radio actuation signals
- Wiper control
- Turn signal flasher audible click
- UConnect(R) Hands-Free, Voice-Actuated Communication system actuation signal (if equipped)
- Display of the outputs for the HomeLink(R) universal home security system and compass (if equipped)
- Key-in-ignition warning chime
- Seat belt warning chime and lamp (Including BeltAlert(R))
- Door ajar warning indicator
- Liftgate/trunk ajar warning indicator

The IC also provides the following enhancements to the above features:

- The improved BeltAlert(R) seatbelt warning indication
- Filtering of input signals to the fuel gauge, temperature gauge, and speedometer to avoid sudden, unexpected pointer movements

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 illumination intensity of the LCD unit is controlled by the IC circuitry based upon an input from the headlamp switch and a dimming level input received from the panel dimmer switch. The IC synchronizes the illumination intensity of other display units with that of the unit in the IC by sending electronic dimming level messages to other electronic modules in the vehicle over the CAN data bus.

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.

The LCD display unit is diagnosed using the IC self-diagnostic actuator test. Testing and Inspection. Proper testing of the CAN data bus and the electronic data bus message inputs to the IC that control some of the LCD functions requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information. Specific operation details for the odometer, the trip odometer, the gear selector indicator, and the various warning and reminder indicator functions of the LCD unit may be found elsewhere in this service 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 vehicles park lamps are on, by rotating the left multifunction dimming control ring (down to dim, up to brighten) to one of five available minor detent positions. The IC monitors a resistor-multiplexed input from the headlamp switch on a dimmer input circuit. In response to that input, the IC electronic circuitry converts a fused 12-volt input it receives on a hard-wired panel lamps dimmer switch signal circuit into a 12-volt Pulse Width Modulated (PWM) output.

The IC uses this PWM output to control the illumination intensity of the cluster, the HVAC rear controls, the window and lock switch back lighting, and the shifter (PRNDL) back lighting. The IC also transmits electronic dimming level messages over the LIN data bus to other electronic modules in the vehicle, such as the Telematics Gateway (TGW), and the Integrated Center Stack (ICS) Screen to control and synchronize their illumination intensity.

In addition, the dimming control ring on the headlamp switch has a Parade Mode position to provide a parade or funeral mode. The IC monitors the request for this mode from the headlamp switch, then transmits an electronic dimming level message to illuminate all LCD unit 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 IC 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 IC over the CAN data bus requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.