Operation

OPERATION

The ElectroMechanical Instrument Cluster (EMIC) in this model also includes the hardware and software necessary to serve as the electronic body control module and is sometimes referred to as the Cab Compartment Node or 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 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 and the Local Interconnect Network (LIN) data bus. The CCN is the master of the LIN bus and there are five modules that talk to the CCN (Smart Glass Module (SGM) - PT27 only, Heated Seat Module (HSM), Remote Compass Module (RCM), Steering Column Control Module (SCCM), and the Accessory Switch Bank Module (ASBM) 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/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 of the instrument panel wire harness.

The CCN also has a self-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 odometer/trip odometer/gear selector indicator Vacuum-Fluorescent Display (VFD) unit and Electronic Vehicle Information Center (EVIC). The EVIC will display the hardware/software version, and the CAN and LIN Vehicle Maintenance Monitor (VMM) used in the CCN.

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.

All of the CCN gauges are stepper motors. The gauges are diagnosed using the CCN self-diagnostic actuator test. Proper testing of the CAN data bus and the electronic data bus message inputs to the CCN that control each gauge require 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.

VACUUM-FLUORESCENT DISPLAYS

The Vacuum-Fluorescent Display (VFD) units are soldered to the CCN electronic circuit board. With the ignition switch in the Off or Accessory positions, the left and right VFD displays are activated when the driver door is opened and is 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 VFD units are 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 VFD 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/LIN data bus.

NOTE: Any time the MIL (yellow) or TPM (yellow) telltales illuminate in the PRNDL/Odometer VF display, the entire display will brighten to FULL DAYTIME INTENSITY. This is so these two telltales won't be able to be dimmed in intensity with the interior lamps dimmer.

The CCN VFD units have several display capabilities. The right VFD unit displays odometer, trip odometer, engine hours, gear selector indication (PRNDL) for models with an automatic transmission, several warning or reminder indications, and various diagnostic information when certain fault conditions exist. An odometer/trip odometer switch on the CCN circuit board is used to control some of the display modes of the right VFD. This switch is actuated manually by depressing the odometer/trip odometer switch button that extends through the lower edge of the cluster lens, just left of the tachometer. Actuating this switch momentarily with the ignition switch in the On position will toggle the VFD between the odometer and trip odometer modes. Depressing the switch button for about two seconds while the VFD is in the trip odometer mode will reset the trip odometer value to zero. The left VFD unit displays the Electronic Vehicle Information Center (EVIC) and Compass/Temperature information. The left switch button is used as a STEP button for the EVIC display and customer programmable features Operation.

Holding the right switch depressed while turning the ignition switch from the Off position to the On position will initiate the CCN self-diagnostic actuator test. Refer to the instrument cluster diagnosis and testing service information for additional details on this cluster function. The CCN microprocessor remembers which display mode is active when the ignition switch is turned to the Off position, and returns the VFD display to that mode when the ignition switch is turned On again.

The VFD unit is diagnosed using the CCN self-diagnostic actuator test. 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.

INDICATORS

Indicators are located in various positions within the CCN and are all connected to the CCN electronic circuit board. The door ajar indicator, cargo lamp indicator, high beam indicator, and turn signal indicators operate based upon hard wired inputs to the CCN. The brake indicator is controlled by CAN data bus messages from the Controller Antilock Brake (CAB) as well as by hard wired park brake switch inputs to the CCN. The driver and passenger seat belt indicator is the same, but the inputs differ. The driver seat belt indicator is controlled by a hard wired seat belt switch input to the CCN. The passenger seat belt indicator is controlled by a CAN data bus message from the Occupant Restraint Controller (ORC). Both seat belt switches are located in the front seat belt retractors. The Malfunction Indicator Lamp (MIL) is normally controlled by CAN data bus messages from the Powertrain Control Module (PCM); however, if the CCN loses CAN data bus communication, the CCN circuitry will automatically turn the MIL on until CAN data bus communication is restored. The CCN uses CAN data bus messages from the Totally Integrated Power Module (TIPM), the ORC, the CAB, and the Sentry Key REmote Entry Module (SKREEM) to control all of the remaining indicators.

The various CCN indicators are controlled by different strategies; some receive fused ignition switch output from the CCN 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 cruise indicator located within the VFD unit is dimmable. All other indicators are illuminated at a fixed intensity, which is not affected by the selected illumination intensity of the CCN general illumination LED's. The illumination intensity of the dimmable indicators is synchronized with that of the CCN general illumination LED's.

In addition, certain indicators in this instrument cluster are automatically configured 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 configured or self-configured indicators remain latent in each CCN at all times and will be active only when the CCN receives the appropriate CAN message inputs for that optional system or equipment.

The hard wired indicator inputs may be diagnosed using conventional diagnostic methods. However, the CCN circuitry and CAN/LIN bus message controlled indicators are diagnosed using the CCN self-diagnostic actuator test. Some indicators are requested to be turned on via the LIN bus. Proper testing of the CAN/LIN data bus and the electronic message inputs to the CCN that control an 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 illumination lamps that are illuminated whenever the exterior lighting is turned On. The illumination intensity of these lamps is adjusted when the interior lighting thumbwheel on the headlamp switch is rotated (down to dim, up to brighten) to one of six available minor detent positions. The CCN monitors a resistor multiplexed input from the headlamp switch on a dimmer input circuit. 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, the instrument panel center stack illumination, and the VFD unit on the CCN circuit board. The CCN also transmits electronic dimming level messages over the LIN data bus to other electronic modules (such as the ASBM, HVAC control head, the radio, and the clock) in the vehicle to control and synchronize their illumination intensity.

In addition, the thumbwheel on the headlamp switch has a Parade Mode position to provide a parade or funeral mode. The CCN monitors the request for this mode from the headlamp switch, then transmits an electronic dimming level message to illuminate all VFD 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 CCN may be diagnosed using conventional diagnostic methods. However, proper testing of the PWM processing of the CCN and the electronic dimming level messages sent by the CCN over the CAN data bus requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.