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Fig. 1 Instrument Cluster:

INSTRUMENT CLUSTER
The instrument cluster for this model is an Electromechanical Instrument Cluster (EMIC) module that is located in the instrument panel above the steering column opening, directly in front of the driver (Fig. 1). The EMIC gauges and indicators are protected by an integral clear plastic cluster lens, and are visible through a dedicated opening in the cluster bezel on the instrument panel. Just behind the cluster lens is the cluster hood and integral cluster mask, which are constructed of molded black plastic. The cluster 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 the define the individual gauges and the information center area of the EMIC. Behind the cluster hood and mask is the cluster overlay and gauges. The overlay is a laminated plastic unit. The dark, visible surface of the outer layer of the overlay is marked with all of the gauge identification 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 under-lying layer of the overlay is opaque and allows light from the various indicators and illumination lamps behind it to be visible through the outer layer of the overlay only through predetermined cutouts. On the lower edge of the cluster lens just left of center, the odometer/trip odometer switch knob protrudes through dedicated holes in the cluster mask and the cluster lens. The remainder of the EMIC, including the mounts and the electrical connections, are concealed behind the cluster bezel. The molded plastic EMIC housing has four integral mounting tabs, two each on the upper and lower edges of the housing. The EMIC is secured to the molded plastic instrument panel cluster carrier with four screws. All electrical connections to the EMIC are made at the back of the cluster housing through two take outs of the instrument panel wire harness, each equipped with a self-docking connector.

A single EMIC module is offered on this model; however, some variations of this module exist due to optional equipment and regulatory requirements. This module utilizes integrated circuitry and information carried on the Programmable Communications Interface (PCI) data bus network for control of all gauges and many of the indicators. (Refer to ELECTRONIC CONTROL MODULES/COMMUNICATION - DESCRIPTION). The EMIC also uses several hard wired inputs in order to perform its many functions. In addition to instrumentation and indicators, the EMIC has hardware and/or software to support the following functions:

- Chime Warning Requests - The EMIC sends chime tone requests over the PCI data bus network to the Central Timer Module (CTM) when it monitors certain conditions or inputs. The CTM replaces the chime or buzzer module and performs the functions necessary to provide audible alerts that are synchronized with the visual alerts provided by the EMIC. (Refer to CHIME/BUZZER - DESCRIPTION).

- Vacuum Fluorescent Display (VFD) Dimming service - The EMIC performs the functions necessary to eliminate the need for a separate VFD dimming module by providing control and synchronization of the illumination intensity of all vacuum fluorescent displays in the vehicle, as well as a parade mode.

The EMIC module incorporates a blue-green digital VFD for displaying odometer and trip odometer information, as well as the amber cruise indicator display function. Some variations of the EMIC are necessary to support optional equipment and regulatory requirements. The EMIC includes the following analog gauges:
- Coolant Temperature Gauge
- Fuel Gauge
- Oil Pressure Gauge
- Speedometer
- Tachometer
- Voltage Gauge

The EMIC also includes provisions for the following indicators:
- Airbag Indicator
- Antilock Brake System (ABS) Indicator
- Brake Indicator
- Check Gauges Indicator
- Cruise Indicator (Odometer VFD)
- Door Ajar Indicator
- High Beam Indicator
- Liftgate Ajar Indicator
- Low Fuel Indicator
- Malfunction Indicator Lamp (MIL)
- Overdrive-Off Indicator
- Seatbelt Indicator
- Security Indicator
- Service Four-Wheel Drive Indicator
- Transmission Overtemp Indicator
- Turn Signal (Right and Left) Indicators
- Washer Fluid Indicator

Some of these indicators are either programmable or automatically configured when the EMIC is connected to the vehicle electrical system. This feature allows those indicators to be activated or deactivated for compatibility with certain optional equipment. The EMIC also incorporates a blue-green digital VFD in the lower right corner of the cluster for displaying the transmission gear that has been selected with the automatic transmission gear selector lever, as well as the amber overdrive-off indicator display function.

Cluster illumination is accomplished by adjustable incandescent back lighting, which illuminates the gauges for visibility when the exterior lighting is turned ON. The EMIC high beam indicator and turn signal indicators are also illuminated by dedicated incandescent bulbs. The remaining indicators in the EMIC are each illuminated by a dedicated Light Emitting Diode (LED) that is soldered onto the electronic circuit board. Each of the incandescent bulbs is secured by an integral bulb holder to the electronic circuit board from the back of the cluster housing.

Hard wired circuitry connects the EMIC to the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the EMIC through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators.

The EMIC modules for this model are serviced only as complete units. The EMIC module cannot be adjusted or repaired. If a gauge, an LED indicator, the VFD, the electronic circuit board, the circuit board hardware, the cluster overlay, or the EMIC housing are damaged or faulty, the entire EMIC module must be replaced. The cluster lens and the hood and mask unit, the rear cluster housing cover, and the incandescent lamp bulbs with holders are available for individual service replacement.

The Electromechanical Instrument Cluster (EMIC) 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 EMIC 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 EMIC 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 EMIC 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 Programmable Communications Interface (PCI) data bus network. (Refer to ELECTRONIC CONTROL MODULES/COMMUNICATION - OPERATION).

The EMIC 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 low/high battery voltage, low oil pressure, or high coolant temperature, the algorithm drives the gauge pointer to an extreme position and the microprocessor turns ON a "Check Gauges" indicator to provide a distinct visual indication of a problem to the vehicle operator. The instrument cluster circuitry may also generate an electronic chime tone request message to the Central Timer Module (CTM) over the PCI data bus when it monitors certain conditions or inputs, in order to provide the vehicle operator with an audible alert to supplement a visual indication. One such alert is a turn signal warning chime, which the EMIC provides by monitoring the turn signal indicators and PCI bus messages from the PCM for vehicle speed and distance. If the EMIC determines that a turn signal is left ON for a distance greater than about 1.6 kilometers (1 mile) at a vehicle speed greater than about 24 km/h (15 mph), it will send an electronic message to the CTM requesting a continuous chime to sound until the turn signal is turned OFF or the vehicle speed is less than 24 km/h (15 mph).

The EMIC circuitry operates on battery current received through a fused B(+) fuse in the Junction Block (JB) on a non-switched fused B(+) circuit, and on battery current received through a fused ignition switch output (RUN/START) fuse in the JB on a fused ignition switch output (RUN/START) circuit. This arrangement allows the EMIC 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 EMIC circuitry is grounded through two separate ground circuits located in one of the two instrument cluster connectors and take outs of the instrument panel wire harness. One ground circuit receives ground through a take out with an eyelet terminal connector of the instrument panel wire harness that is secured by a nut to a ground stud located on the left cowl side inner panel below the instrument panel, while the other ground circuit receives ground through a take out with an eyelet terminal connector of the headlamp and dash wire harness that is secured by a nut to a ground stud located on the left front fender inner shield near the battery in the engine compartment.

The EMIC also has a self-diagnostic actuator test capability, which will test each of the PCI bus message-controlled functions of the cluster by lighting the appropriate indicators and positioning the gauge needles at several predetermined locations on the gauge faces in a prescribed sequence. (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). See the owner's manual in the vehicle glove box for more information on the features, use and operation of the EMIC.

Gauges
All gauges receive battery current through the EMIC circuitry 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 EMIC 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 EMIC gauges, except the odometer, are air core magnetic units. Two fixed electromagnetic coils are located within each gauge. These coils are wrapped at right angles to each other around a movable permanent magnet. The movable magnet is suspended within the coils on one end of a pivot shaft, while the gauge needle is attached to the other end of the shaft. One of the coils has a fixed current flowing through it to maintain a constant magnetic field strength. Current flow through the second coil changes, which causes changes in its magnetic field strength. The current flowing through the second coil is changed by the EMIC circuitry in response to messages received over the PCI data bus. The gauge needle moves as the movable permanent magnet aligns itself to the changing magnetic fields created around it by the electromagnets.

The gauges are diagnosed using the EMIC self-diagnostic actuator test. (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). Proper testing of the PCI data bus and the data bus message inputs to the EMIC that control each gauge require the use of a DRB III scan tool. Refer to the appropriate diagnostic information. Specific operation details for each gauge may be found elsewhere.

Vacuum-fluorescent Display
The Vacuum-Fluorescent Display (VFD) module is soldered to the EMIC circuit board. The display is active with the ignition switch in the ON or Start positions, and inactive when the ignition switch is in any other position. The VFD has several display capabilities including odometer, trip odometer, and an amber "CRUISE" indication whenever the optional speed control system is turned ON. The cruise indicator function of the VFD is automatically enabled or disabled by the EMIC circuitry based upon whether the vehicle is equipped with the speed control option. An odometer/trip odometer switch ON the EMIC circuit board is used to control several of the display modes. 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 center. Actuating this switch momentarily with the ignition switch in the ON position will toggle the VFD between the odometer and trip odometer modes. The word "TRIP" will also appear in blue-green text when the VFD trip odometer mode is active. 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. Holding this switch depressed while turning the ignition switch from the OFF position to the ON position will activate the EMIC self-diagnostic actuator test. The EMIC will automatically flash the odometer or trip odometer information ON and OFF if there is a loss of PCI data bus communication. The VFD will also display various information used in several diagnostic procedures. Refer to the appropriate diagnostic information for additional details on this VFD function.

The EMIC also has a second VFD soldered to the EMIC circuit board, which serves as the electronic transmission gear selector indicator. Like the odometer/trip odometer VFD, this display is active with the ignition switch in the ON or Start positions, and inactive when the ignition switch is in any other position. This VFD also has an amber "O/D OFF" indicator that illuminates when the automatic transmission electronic overdrive is turned OFF by depressing the overdrive-off switch button located in the knob on the end of the gear selector lever on the right side of the steering column. This VFD displays the characters "P,", "R," "N," "D," "2,"and "1," which represent each of the available gear selector positions. A small rectangular box is illuminated around the character representing the gear position that is currently selected.

Both VFDs are diagnosed using the EMIC self-diagnostic actuator test. (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). Proper testing of the PCI data bus and the data bus message inputs to the EMIC that control some of the VFD functions requires the use of a DRB III scan tool. Refer to the appropriate diagnostic information. Specific operation details for the odometer, trip odometer, gear selector indicator, cruise indicator, and overdrive-off indicator functions of these VFDs may be found elsewhere.

Indicators
Indicators are located in various positions within the EMIC and are all connected to the EMIC circuit board. The high beam indicator, washer fluid indicator, and turn signal indicators are hard wired. The brake indicator is controlled by Pd data bus messages from the Controller Anti-lock Brake (CAB) and the hard wired park brake switch input to the EMIC. The seatbelt indicator is controlled by the EMIC programming, PCI data bus messages from the Airbag Control Module (ACM), and the hard wired seat belt switch input to the EMIC. The security indicator is controlled by a hard wired Central Timer Module (CTM) input to the EMIC, and by PCI data bus messages from the Sentry Key Immobilizer Module (SKIM) if the vehicle is equipped with the optional Sentry Key Immobilizer System (SKIS). The Malfunction Indicator Lamp (MIL) is normally controlled by PCI data bus messages from the Powertrain Control Module (PCM); however, if the EMIC loses PCI data bus communications, the EMIC circuitry will automatically turn the MIL ON, and flash the odometer VFD ON and off repeatedly until PCI data bus communication is restored. The EMIC uses PCI data bus messages from the CTM, the PCM, the Transfer Case Control Module (TCCM), the ACM, and the CAB to control all of the remaining indicators. Different indicators are controlled by different strategies; some receive fused ignition switch output from the EMIC circuitry cluster and have a switched ground, while others are grounded through the EMIC circuitry and have a switched battery feed.

In addition, certain indicators in this instrument cluster are configurable. This feature allows the configurable indicators to be automatically enabled or disabled by the EMIC circuitry for compatibility with certain optional equipment. The cruise indicator, service 4WD indicator, gear selector indicator, overdrive- off indicator, and the transmission overtemp indicator are automatically configured, either electronically or mechanically. If the EMIC is disconnected from the fused B(+) circuit for more than about five minutes the EMIC will forget its previous electronic configuration settings, but will learn the proper indicator configuration settings again when it is reinstalled in a vehicle.

The hard wired indicators are diagnosed using conventional diagnostic methods. The EMIC and PCI bus message controlled indicator lamps are diagnosed using the EMIC self-diagnostic actuator test. (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). Proper testing of the PCI data bus and the data bus message inputs to the EMIC that control each indicator require the use of a DRB III scan tool. Refer to the appropriate diagnostic information. Specific operation details for each indicator may be found elsewhere.

Cluster Illumination
The EMIC has several illumination lamps that are illuminated when the exterior lighting is turned ON with the headlamp switch. The illumination brightness of these lamps is adjusted by the panel lamps dimmer rheostat when the headlamp switch thumb-wheel is rotated (down to dim, up to brighten). The illumination lamps receive battery current through the panel lamps dimmer rheostat and a fuse in the JB on a fused panel lamps dimmer switch signal circuit. The illumination lamps are grounded at all times.

In addition, an Analog/Digital (A/D) converter in the EMIC converts the analog panel lamps dimmer rheostat input from the headlamp switch to a digital dimming level signal for controlling the lighting level of the VFD. The EMIC also broadcasts this digital dimming information as a message over the PCI data bus for use by the Compass Mini-Trip Computer (CMTC) in synchronizing the lighting level of its VFD with that of the EMIC. The headlamp switch thumbwheel also has a Parade position to provide a parade mode. The EMIC monitors the request for this mode through a hard wired day brightness sense circuit input from the headlamp switch. In this mode, the EMIC Will override the selected panel dimmer switch signal and send a message over the PCI data bus to illuminate all vacuum fluorescent displays at full brightness for easier visibility when driving in daylight with the exterior lighting turned ON. The parade mode has no effect on the incandescent bulb illumination intensity.

The hard wired cluster illumination lamps are diagnosed using conventional diagnostic methods. Proper testing of the VFD dimming level and the PCI data bus dimming level message functions requires the use of a DRB III scan tool. Refer to the appropriate diagnostic information.

Chime Warning Requests
The EMIC is programmed to request chime service from the Central Timer Module (CTM) when certain indicator lamps are illuminated. When the programmed conditions are met, the EMIC generates an electronic chime request message and sends it over the PCI data bus to the CTM. Upon receiving the proper chime request message, the CTM activates an integral chime tone generator to provide the audible chime tone to the vehicle operator. (Refer to CHIME/BUZZER - OPERATION). Proper testing of the EMIC, the CTM and the PCI data bus chime request message functions requires the use of a DRB III scan tool. Refer to the appropriate diagnostic information.