Instrument Cluster - Operation

OPERATION - LHD

The Instrument Cluster in this vehicle includes the hardware and software necessary to serve as the electronic body control module that is 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 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 display 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

The Vacuum-Fluorescent Display (VFD) units are soldered to the CCN electronic circuit board. Both the standard odometer and gear selector indicator VFD unit and the optional Compass Mini Trip Computer (CMTC) VFD unit are fixed segment dot matrix displays. The optional Electronic Vehicle Information Center (EVIC) VFD unit is a reconfigurable dot matrix display. With the ignition switch in the OFF or ACCESSORY positions, all VFD displays are deactivated. The total odometer information is displayed when the driver door is opened (Rental Car Mode) and is deactivated when the driver door is closed or after five minutes, whichever occurs first. Otherwise, all VFD 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 is controlled by the CCN circuitry based upon electronic dimming level messages received over the CAN data bus indicating the exterior lighting is turned ON and the dimming level selected using the panel dimmer function of the thumbwheel on the headlamp switch. The illumination intensity of the CCN VFD units is synchronized with that of other display units in the vehicle by sending the same electronic dimming level message inputs to all electronic modules in the vehicle over the CAN or LIN data bus.

The odometer VFD unit has several display capabilities including odometer, trip odometer A and B, the cruise indicator, gear selector indicator, several textual warning or reminder indications, and various diagnostic information when certain fault conditions exist. The optional CMTC VFD unit displays compass, temperature, average fuel economy, distance to empty, elapsed time and cycles the optional park assist feature ON or OFF. The display options for these VFD units are selected using switches on the CCN circuit board that are actuated using push buttons adjacent to the displays. The optional EVIC VFD unit displays several textual warning or reminder indications, compass, temperature, average fuel economy, distance to empty, elapsed time, audio settings and provides a customer programmable features interface. The EVIC display options are selected using steering wheel-mounted switches.

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-test Testing and Inspection. 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.

Actuating the right CMTC push button momentarily with the ignition switch in the ON position will toggle the CMTC VFD between the various display functions, and actuating the left CMTC push button toggles the display between standard and metric units. The CCN microprocessor remembers which 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.

All instrument cluster VFD units are diagnosed using the instrument cluster self-test Testing and Inspection. 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 instrument cluster 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 thumbwheel on the headlamp switch is rotated to one of six available minor detent positions. The CCN monitors a hard-wired multiplexed input received from the headlamp switch on the instrument panel 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.