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 EMIC are found within the Chime/Buzzer service information.

The CCN 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 CCN 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 CCN 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 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 CCN 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 actuator 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 two Organic Light Emitting Diode (OLED) display units. Invoking the actuator test requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

GAUGES

All gauges receive battery current through the CCN circuitry only when the ignition switch is in the ON or START positions. With the ignition switch in the OFF position battery current is not supplied to any gauges, and the CCN circuitry is programmed to move all of the gauge needles back to the low end of their respective scales. Therefore, the gauges do not accurately indicate any vehicle condition unless the ignition switch is in the ON or START positions.

Each of the CCN gauges contains an electronically controlled stepper motor unit. The CCN circuitry completely controls the activation and deactivation of these stepper motors to position each gauge needle in the appropriate position based upon cluster programming and electronic messages received over the CAN data bus.

The gauges are diagnosed using the diagnostic self test. Invoking the actuator test as well as proper testing of the CAN data bus and the electronic data bus message inputs to the CCN that control each gauge requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information. Specific operation details for each gauge may be found elsewhere in this service information.

ORGANIC LIGHT EMITTING DIODE DISPLAYS

Two Organic Light Emitting Diode (OLED) display units are soldered to the CCN electronic circuit board. The one below the speedometer is a fixed segment display, while the one below the tachometer is a reconfigurable dot matrix display. With the ignition switch in the OFF or ACCESSORY positions, the fixed segment OLED display is activated and the total odometer information is displayed when either front door is opened (Rental Car mode), and is deactivated after both front doors are closed or after five minutes, whichever occurs first. Otherwise, both 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 OLED display units is controlled by the CCN circuitry based upon electronic dimming level messages received over the LIN data bus indicating the exterior lighting is turned ON and the dimming level selected using the panel dimmer function of the control sleeve on the control stalk of the left (lighting) multi-function switch. The illumination intensity of the CCN OLED displays is synchronized with that of other display units in the vehicle by transmitting electronic dimming level messages as inputs to all electronic modules in the vehicle over the CAN or LIN data bus.

The fixed segment OLED unit has several display capabilities including odometer, gear selector indication (PRNDL) and the cruise indicator. The reconfigurable dot matrix OLED unit displays numerous warning or reminder textual messages, all Electronic Vehicle Information Center (EVIC) data including compass, temperature, trip computer, trip odometer A and B, maintenance reminders, the customer programmable features interface and various diagnostic information when certain fault conditions exist. The buttons in the upper instrument panel switch pod above the heater and air conditioner controls in the instrument panel center stack area are used to control many of the display modes for the reconfigurable dot matrix OLED unit.

Actuating the STEP switch button momentarily with the ignition switch in the ON position will toggle the dot matrix OLED between the trip odometer A or B modes, the various trip computer functions and the various customer programmable feature selectors. Depressing the RESET switch button for about two seconds while the OLED is displaying one of the trip odometer modes will reset that trip odometer value to zero. The CCN microprocessor remembers which display modes are active when the ignition switch is turned to the OFF position, and returns the display to that mode when the ignition switch is turned ON again.

Both OLED units are diagnosed using the diagnostic self test. Invoking the actuator test as well as proper testing of the CAN data bus, the LIN data bus and the electronic data bus message inputs to the CCN that control each OLED display function 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, the EVIC and the various warning and reminder textual message indicator functions of the OLED display units may be found elsewhere in this service information.

INDICATORS

Indicators are located in various positions within the CCN and are all connected to the CCN electronic circuit board. Some indicators operate based upon hard wired inputs to the CCN, but most are controlled by CAN or LIN data bus messages from other electronic modules in the vehicle. Some are controlled by a combination of hard wired inputs, electronic messaging and CCN programming. If the CCN loses CAN data bus communication, the CCN circuitry will automatically turn ON the Malfunction Indicator Lamp (MIL) until CAN data bus communication is restored.

The various CCN indicators are controlled by different strategies; some receive fused ignition switch output from the EMIC circuitry and have a switched ground, while others are grounded through the CCN circuitry and have a switched battery feed. However, all indicators are completely controlled by the CCN microprocessor based upon various hard wired and electronic message inputs. The high beam, front and rear fog lamp, 4WD low, and tow/haul indicators and those located within an OLED display are dimmable. All other indicators are illuminated at a fixed intensity, which is not affected by the selected illumination intensity of the CCN general illumination lighting. The illumination intensity of the dimmable indicators is synchronized with that of the general illumination lighting.

In addition, certain indicators in this instrument cluster are automatically or self-configured. This feature allows the configurable indicators to be enabled by the CCN circuitry for compatibility with certain optional equipment. The CCN defaults for the ABS indicator and airbag indicator are enabled, and these configuration settings must be programmatically disabled in the CCN using a diagnostic scan tool for vehicles that do not have this equipment. The automatically or self-configured indicators remain latent in each CCN at all times and will be active only when the CCN receives the appropriate CAN bus or LIN bus message inputs for that optional system or equipment.

The hard wired indicator inputs may be diagnosed using conventional diagnostic tools and procedures. However, the CCN circuitry and CAN or LIN bus message controlled indicators are diagnosed using the diagnostic self test. Invoking the actuator test as well as proper testing of the CAN data bus, the LIN data bus and the electronic data bus message inputs to the CCN that control each indicator requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information. Specific details of the operation for each indicator may be found elsewhere in this service information.

CLUSTER ILLUMINATION

The CCN has several Light Emitting Diode (LED) units that provide cluster back lighting whenever the exterior lighting is turned ON for Laredo vehicles, or whenever the ignition switch is in the ON position on Limited and Overland vehicles. 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 OLED 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 hardwired 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.