Instrument Cluster - Operation

OPERATION

The instrument cluster in this vehicle includes the hardware and software necessary to serve as the electronic body control module and is sometimes referred to as the Cab Compartment Node (CCN). The following information deals primarily with the instrument cluster functions of this unit. Additional details of the electronic body control functions of this unit may be found within the service information for the system or component that the CCN controls. For example: Additional details of the audible warning functions of the CCN are found within the Chime/Buzzer service information.

The instrument cluster 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 cluster 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 instrument cluster is positioned 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 microprocessor-based CCN 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 or the Local Interface Network (LIN) data bus. Communication - Operation.

The CCN 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 a chime through the on-board audible tone transducer to provide distinct visual and audible indications of a problem to the vehicle operator. The CCN may also produce audible warnings for other electronic modules in the vehicle based upon electronic tone request messages received over the CAN or LIN data bus. Each audible warning is intended to provide the vehicle operator with an audible alert to supplement a visual indication.

The 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 CCN 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 CCN circuitry is grounded through a ground circuit and take out of the instrument panel wire harness with an eyelet terminal connector that is secured by a ground screw to a ground location near the left end of the instrument panel structural support.

The CCN also has a diagnostic self test capability, which will test each of the CAN bus message-controlled functions of the cluster by lighting the appropriate indicators, positioning the gauge needles at several predetermined calibration points across the gauge faces, and illuminating all segments of the Liquid Crystal Display (LCD) units. For more information on the diagnostic self test, Testing and Inspection.

LIQUID CRYSTAL DISPLAY

The LCD unit is an integrated part of the CCN and is soldered to the electronic circuit board. With the ignition switch in the OFF or ACCESSORY positions, the odometer display is activated when the driver door is opened (Rental Car mode) and is deactivated when the driver door is closed. Otherwise, the display unit is 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 LCD has several display capabilities including odometer, trip odometer, engine hours, gear selector indication (PRNDL), several warning or reminder indications, and various diagnostic information when certain fault conditions exist.

Dual trip odometer (Trip A and Trip B) capability is standard equipment on this vehicle. Both trip odometers appear within the LCD display unit, although they cannot be displayed simultaneously. The trip odometer information is stored in the instrument cluster memory. Each trip odometer can display values up to 16099.9 kilometers (9999.9 miles). Each trip odometer will roll over to zero independently when it accumulates these values. The trip odometer minimum value is 0.0 (miles or kilometers) and does have a decimal point to show tenths of a full unit values (miles or kilometers).

The buttons in the left side of the steering wheel control many of the display modes for the EVIC. Actuating the SCROLL buttons momentarily with the ignition switch in the ON position will toggle the display to the trip info menu. With Trip info highlighted, press the STEP bottom momentarily to enter the trip menu. Select TRIP A or TRIP B, depressing the STEP button for about two seconds while one of the trip odometer modes is displayed will reset that trip odometer value to zero. To return, press the BACK button, scroll through the main menu to turn menu off and press the step button.

The LCD unit can be diagnosed using the CCN self-diagnostic test Testing and Inspection. Proper testing of the CAN data bus and the electronic data bus message inputs to the CCN that control some of the VFD 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 VFD unit may be found elsewhere in this service information.

CLUSTER ILLUMINATION

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

The CCN has several Light Emitting Diode (LED) units that provide cluster back lighting whenever the exterior lighting is turned ON, or whenever the ignition switch is in the ON position. The illumination intensity of these LED units is adjusted when the panel lamps dimmer function of the control sleeve on the control stalk of the left (lighting) multi-function switch is rotated to one of six available minor detent positions. The CCN monitors an electronic dimming level message input received over the LIN data bus from the Steering Control Module (SCM) to determine the selected lighting level. In response to that input, the CCN 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 CCN uses this PWM output to control the illumination intensity of the cluster general illumination lighting and the LCD display units on the CCN circuit board, then provides a synchronized PWM output on various hard-wired fused panel lamps dimmer switch signal circuits to control and synchronize the illumination intensity of other incandescent illumination lamps in the vehicle. The CCN also transmits electronic dimming level messages over the CAN data bus to other electronic modules in the vehicle to control and synchronize the illumination intensity of their display units to that of the CCN displays.

The hard-wired panel lamps dimmer outputs from the CCN may be diagnosed using conventional diagnostic tools and procedures. However, proper testing of the PWM processing of the CCN and the electronic dimming level messages received by the CCN over the LIN data bus requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.