Instrument Cluster - Description
DESCRIPTION
The instrument cluster (2), located in the instrument panel above the steering column is only visible through an opening in the cluster bezel (1). The main body of the instrument cluster, including the mounts and the electrical connections, are concealed within the instrument panel behind the cluster bezel. The instrument cluster for this vehicle also includes the hardware and software necessary to serve as the electronic body control module known as the Cab Compartment Node or (CCN).
Besides analog gauges and indicators, the instrument cluster incorporates one of two available blue-green digital Vacuum Fluorescent Display (VFD) units. The standard VFD unit is for displaying odometer information, automatic transmission gear selector position (PRNDL), and several other indicators. The optional display unit is a Compass and Mini Trip Computer (CMTC) and is discussed elsewhere. For more information on the CMTC Compass And Mini-Trip Computer Module - Description
The instrument cluster gauges and Light Emitting Diode (LED) indicators, are visible through a dedicated opening in the instrument panel behind the cluster bezel, and are protected by a clear plastic cluster lens (5). Just behind the cluster lens is the cluster hood and integral mask (3). The hood, serves as a visor and shields the face of the cluster from ambient light and reflections to reduce glare, while the cluster mask serves to separate and define the individual gauges from the indicator areas and trims the outside perimeter of the cluster overlay. The mask is constructed of black molded plastic, and is sometimes painted silver on vehicles with certain optional trim packages. The hood and mask, as well as the cluster lens are secured through integral latch features that secure it to the outer perimeter of the cluster housing (2). The hood and mask unit also has two integral mounting tabs on the lower corners that combine with the tabs integral to the cluster housing to secure the bottom of the CCN to the molded plastic instrument panel cluster carrier, with two fasteners.
The rear of the cluster housing and the CCN electronic circuitry are protected by a molded white plastic rear cover (1), which is also secured to the cluster housing by integral latch features. The rear cover includes clearance holes for the four CCN connector receptacles. The connector receptacles on the back of the CCN electronic circuit board connect the unit to the vehicle's electrical system through four electrical take outs from the instrument panel wire harness.
Sandwiched between the rear cover and the lens and hood unit is the cluster housing. The molded white plastic cluster housing serves as the carrier for the instrument cluster circuitry, the cluster gauge set, the indicator LED's, the VFD display units as well as an audible tone transducer and general cluster illumination LED's. The standard equipment molded black plastic odometer/trip odometer switch button as well as the optional CMTC display switch button extend from the face of the cluster housing through dedicated holes in the cluster mask and the cluster lens adjacent to their respective VFD units. A black rubber boot (4) seals each switch button to the clearance hole in the lens.
The cluster overlay is a laminated plastic unit. The dark, visible, outer surface of the overlay is marked with all of the gauge dial faces and graduations, but this layer is also translucent. The darkness of this outer layer prevents the cluster from appearing cluttered or busy by concealing the cluster indicators that are not illuminated, while the translucence of this layer allows those indicators and icons that are illuminated to be readily visible. The underlying layer of the overlay is opaque and allows light from the indicator LED's to be visible through the outer layer of the overlay through predetermined stencil-like cutouts. Openings in the overlay at the base of the speedometer and tachometer dial faces have smoked clear lenses through which the illuminated VFD units can be viewed.
Several versions of the CCN module are offered on this vehicle. These versions accommodate all of the variations of optional equipment and regulatory requirements for the various markets in which the vehicle is offered. The microprocessor-based CCN utilizes integrated circuitry and information carried on the Controller Area Network (CAN) data bus and the Local Interface Network (LIN) data bus along with several hard wired analog and multiplexed inputs to monitor sensors and switches throughout the vehicle. In response to those inputs, the internal circuitry and programming of the CCN allow it to control and integrate many electronic functions and features of the vehicle through both hard wired outputs and the transmission of electronic message outputs to other electronic modules in the vehicle over the CAN and LIN data busses. Communication - Description for more information on the CAN and LIN data busses.
VEHICLE SYSTEMS SUPPORT
Besides typical instrument cluster gauge and indicator support, the electronic functions and features that the CCN supports or controls include the following:
- A/C Select and Evaporator Probe Support - The CCN monitors hard wired inputs from the A/C select switch and evaporator temperature sensor inputs, then transmits electronic A/C clutch request messages over the CAN data bus when appropriate to support the A/C clutch control feature.
- Audible Warnings - The CCN electronic circuit board is equipped with an audible tone transducer and programming that allows it to provide various audible alerts to the vehicle operator. These alerts include single chime tones and continuous slow or fast tones. An electromechanical relay is also soldered onto the circuit board to produce audible clicks that are used to emulate the sound of a conventional turn signal or hazard warning flasher.
- Compass Mini-Trip Computer Display Support - The CCN provides support for each of the functions and features of the Compass-Mini-Trip Computer (CMTC) display. This includes support for the compass, thermometer, trip computer and the switch inputs that are used to control and configure many of the displays. This also includes display arbitrator programming, which controls the priorities, sequences, and transition of information that is displayed in the CMTC display, particularly when multiple display requests are received simultaneously.
- Electric Backlight Support - The CCN monitors Electric Backlight (EBL) switch hard wired inputs from the air conditioner-heater control, then transmits the appropriate electronic EBL request messages over the CAN data bus to support the EBL function.
- Enhanced Accident Response Support - The CCN monitors inputs from the Occupant Restraint Controller (ORC) and the Powertrain Control Module (PCM) to automatically turn ON the interior lighting after an airbag deployment event, 10 seconds after the vehicle speed is zero. The interior lighting remains illuminated until the key is removed from the ignition switch lock cylinder, at which time the interior lighting returns to normal operation and control. These Enhanced Accident Response System (EARS) features are each dependent upon a functional vehicle electrical system following the vehicle impact event.
- Exterior Lighting Switch Support - The CCN monitors electronic exterior lighting switch, and turn signal switch status messages from the Steering Control Module (SCM) on the steering column over the LIN data bus and transmits the appropriate electronic exterior lighting and turn signal request messages to the Totally Integrated Power Module (TIPM) over the CAN data bus to support the exterior lighting functions.
- Four Wheel Drive (4WD) Lock Switch Support - The CCN monitors a hard wired input from the 4WD Lock switch on the center floor console then transmits the appropriate electronic 4WD Lock request and Unlock request messages to the Totally Integrated Power Module (TIPM) over the CAN data bus to support the 4WD Lock mode functions.
- Horn Switch Support - The CCN receives a hard wired input from the horn switch on the steering wheel then provides electronic horn request messages over the CAN data bus to support the horn function.
- Interior Lamp Load Shedding - The CCN provides a battery saver feature which will automatically turn OFF all interior lamps if they remain ON after a timed interval of about ten minutes.
- Interior Lighting Control - The CCN monitors electronic messages and hard wired inputs from the interior lighting switch, the door ajar switches, the liftgate ajar switch, the reading lamp switches, and the Wireless Control Module (WCM) to provide courtesy lamp control. This includes support for timed illuminated entry with theater-style fade-to-OFF and courtesy illumination DEFEAT features.
- Local Interface Network Master Module - The CCN is the master module for the LIN data bus. In this role it gathers information from the compass sensor, the Heated Seat Module (HSM), the instrument panel switch pod and the SCM, then either acts on that information directly or places electronic messages on the CAN data bus for use by other modules
- Panel Lamps Dimming Control - The CCN monitors electronic dimming level messages received from the panel lamps dimmer switch input to the SCM over the LIN data bus, then provides both a hard wired 12-volt Pulse-Width Modulated (PWM) output and electronic message outputs over the LIN data bus that synchronizes the dimming level of all panel lamps dimmer controlled lamps with that of the cluster general illumination lighting.
- Wiper and Washer Switch Support - The CCN monitors electronic wiper switch and washer switch status messages from the SCM on the steering column over the LIN data bus and transmits the appropriate electronic wiper and washer request messages to the TIPM over the CAN data bus to support the wiper and washer system functions, including the headlamps-on with wipers programmable feature.
VACUUM-FLUORESCENT DISPLAYS
The Vacuum-Fluorescent Display (VFD) (25)(34) units are soldered to the CCN electronic circuit board. Both the standard one located below the tachometer and the optional Compass Mini-Trip Computer (CMTC) display located below the speedometer are fixed segment displays.
The odometer and trip odometer information are stored in the instrument cluster memory. This information can be increased when the proper inputs are provided to the instrument cluster, but the information cannot be decreased. The odometer can display values up to 999,999 kilometers (999,999 miles). The odometer latches at these values, and will not roll over to zero. The trip odometer can display values up to 999.9 kilometers (999.9 miles) before it rolls over to zero.
The odometer display does not show leading zeroes, does not have a decimal point and will not show values less than a full unit (kilometer or mile). The unit of measure (km or miles) for the odometer display is not shown in the VFD. The unit of measure for the instrument cluster odometer/trip odometer is selected at the time that it is manufactured, and cannot be changed.
The illumination intensity of the VFD units is controlled by the CCN circuitry based upon electronic dimming level messages received over the Controller Area Network (CAN) 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 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 Local Interface Network (LIN) data bus. However, on domestic market vehicles only, if the Tire Pressure Monitor (TPM) indicator or Malfunction Indicator Lamp (MIL) is active, the odometer VFD will illuminate at full daytime brightness until both the TPM indicator and the MIL are extinguished.
During daylight hours (exterior lamps are OFF) the odometer VFD is illuminated at full brightness for clear visibility. At night (exterior lamps are ON), the VFD lighting level is adjusted with the other cluster general illumination lamps using the panel lamps dimmer function of the interior lighting control sleeve on the left multi-function switch control stalk. However, a PARADE mode position of the control sleeve allows the VFD to be illuminated at full brightness if the exterior lamps are turned ON during daylight hours. On vehicles manufactured for domestic markets, the odometer VFD is also illuminated at full brightness whenever the MIL indicator is illuminated, and cannot be dimmed until the MIL indicator is extinguished.
The odometer VFD unit has several display capabilities including odometer, trip odometer A and B, gear selector indication (PRNDL) for vehicles with an automatic transmission, several warning or reminder indications, and various diagnostic information when certain fault conditions exist. On vehicles not equipped with the optional CMTC, the odometer display toggles to an outside temperature display following Trip B. The CMTC VFD unit displays numerous warning or reminder textual messages, all CMTC data including compass, temperature, trip computer, the customer programmable features interface and various diagnostic information when certain fault conditions exist. An odometer/trip odometer switch and a CMTC display switch on the CCN circuit board are used to control many of the display modes of the VFD units. These switches are actuated manually by depressing the odometer/trip odometer or CMTC push button that extends through the lower edge of the cluster lens, adjacent to the VFD that it controls.
The instrument cluster gauges, indicators, VFD units, as well as the cluster illumination are all integral components of the CCN and its electronic circuit board. If any part of the internal working components of the instrument cluster become damaged or ineffective, the entire instrument cluster assembly must be replaced. The cluster lens and the cluster hood and mask unit are the only components of the instrument cluster assembly that can be serviced separately.