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 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 display 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 instrument 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 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. The CCN is the master node for the 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 on the instrument panel structural support.

The CCN also has a self-diagnostic test capability, which will test each of the CAN or LIN 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 Vacuum-Fluorescent Display (VFD) units. Testing and Inspection.

VACUUM-FLUORESCENT DISPLAYS

With the ignition switch in the OFF or ACCESSORY positions, both VFD displays are activated and the total odometer information is displayed when the driver door is opened (Rental Car Mode) and are deactivated when the driver door is 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.

- Odometer/Trip Odometer Display Toggling - Actuating the odometer/trip odometer push button momentarily with the ignition switch in the ON position will toggle the odometer VFD between the odometer and trip odometer modes. Depressing the odometer/trip odometer push button for about two seconds while the VFD is in the trip odometer mode will reset the trip odometer value to zero. Holding the odometer/trip odometer push button depressed while turning the ignition switch from the OFF position to the ON position will initiate the instrument cluster self-diagnostic test. Testing and Inspection for additional details. The CCN microprocessor remembers which odometer display mode is 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
- Trip Odometer Reset - When the trip odometer reset switch button is pressed and held for longer than about two seconds with the ignition switch in the ON or START positions, the trip odometer will be reset to 0.0 kilometers (miles). The VFD must be displaying the trip odometer information in order for the trip odometer information to be reset.
- GasCap Message Display - On vehicles manufactured with a United States country code, each time the cluster receives an electronic message from the PCM indicating a monitored leak in the evaporative emissions system, the cluster replaces the displayed odometer/trip odometer value with the textual message, gascap. This message serves as a reminder to the vehicle operator to check that the gas cap is properly installed and tightened, but could also indicate another source of air leakage in the on-board evaporative and vapor recovery emissions systems. Unless the leak is corrected, this message will latch and remain displayed during the current and each subsequent ignition cycle until the trip odometer reset button is pressed and released momentarily, which will revert the display to the odometer/trip odometer information that was last displayed for the remainder of that ignition cycle. Once the source of a leak has been corrected, either momentarily pressing the trip odometer reset button or cycling the ignition switch will unlatch the message and return the odometer/trip odometer to normal operation.
- Communication Error - If the cluster fails to receive an electronic distance message during normal operation, it will hold and display the last data received until the ignition switch is turned to the OFF position. If the cluster does not receive a distance message within one second after the ignition switch is turned to the ON position, it will display the last distance value stored in the cluster memory. If the cluster is unable to display odometer information due to an error internal to the cluster, the VFD will display error.

The PCM continually monitors the vehicle speed pulse information received from the wheel speed sensors, then sends the proper messages to the CCN. For proper diagnosis of the wheel speed sensors, the PCM, the CCN, the CAN data bus or the electronic communication related to odometer/trip odometer operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.
Proper testing of the CAN or LIN 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.

CLUSTER ILLUMINATION

The CCN has several Light Emitting Diode (LED) units that provide cluster back lighting whenever the exterior lighting is turned ON. 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 VFD 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 and LIN 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.