Part 1A

Fig.1 Instrument Cluster:

INSTRUMENT CLUSTER
The instrument cluster for this model is an Electro Mechanical 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 trims the outside perimeter of the cluster overlay. Behind the cluster hood and mask is the cluster overlay and gauges. The overlay is a laminated plastic unit. The dark, visible, outer surface 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 underlying 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 mask only through predetermined stencil-like cutouts. On the lower edge of the cluster lens just right of center, a small molded rubber odometer/trip odometer switch knob boot covers the switch knob and seals the hole in the lens through which the knob protrudes. 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 on the lower edge of the housing and one on each side. The EMIC is secured to the instrument panel structural support with four screws. All electrical connections to the EMIC are made at the back of the cluster housing through two color-coded connector receptacles that connect the cluster to the vehicle electrical system through two take outs and connectors of the instrument panel wire harness.

Electro-Mechanical Instrument Cluster (EMIC):

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 ELECTRICAL / 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 Service - The EMIC performs the functions necessary to provide audible alerts to the vehicle operator and eliminates the need for a separate chime module. (Refer to ELECTRICAL / CHIME / BUZZER - DESCRIPTION).

- Interior Lighting Control Service - The EMIC performs the functions necessary to provide control of the interior lighting. This control includes providing illuminated entry, fade-to-off (theater) dimming, and battery saver (load shedding) features for all interior courtesy lighting.

- Rear Window Defogger Control and Timer Service - The EMIC performs the functions necessary to control and time the output to the rear window defogger on vehicles so equipped and eliminates the need for a separate control and timer module for the rear window defogger system. (Refer to ELECTRICAL / WINDOW DEFOGGER - DESCRIPTION).

- Vacuum Fluorescent Display (VFD) and Panel Lamps Dimming Service - The EMIC performs the functions necessary to eliminate the need for a separate dimming module. The cluster converts an analog input signal from the headlamp and panel lamps dimmer switches to the appropriate digital, pulse-width modulated outputs to control the dimming levels of both the instrument cluster and radio VFDs as well as the incandescent cluster and panel illumination lighting. This includes providing features such as VFD illumination when a door is ajar, radio illumination control, a parade mode, and dimmable cruise, four-wheel drive, and upshift indicators.

The EMIC module incorporates a blue-green electronic digital VFD for displaying odometer, trip odometer, and diagnostic information. 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
- Fog Lamp (Front or Rear) Indicator
- Four-Wheel Drive (Part Time and/or Full Time) Indicator
- High Beam Indicator
- Low Fuel Indicator
- Malfunction Indicator Lamp (MIL)
- Seatbelt Indicator
- Sentry Key Immobilizer System (SKIS) Indicator
- Turn Signal (Right and Left) Indicators
- Upshift Indicator (Manual Transmission)

Some of these indicators are 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 uses electronic messages received over the PCI data bus from the Airbag Control Module (ACM), the Sentry Key Immobilizer Module (SKIM), and the Powertrain Control Module (PCM) to learn whether the vehicle is equipped with airbags, the Sentry Key Immobilizer System (SKIS), or cruise control; then, configures the appropriate indicators accordingly. Once the EMIC learns that a vehicle has these equipment options installed, these indicators will function accordingly for the remainder of the cluster life.

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 is illuminated by a dedicated incandescent bulb. 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. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.

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, the cluster hood and mask unit, the rear cluster housing cover, the odometer/trip odometer switch knob boot, and the incandescent lamp bulbs with holders are available for individual service replacement.

The Electro Mechanical 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 Commutations Interface (PCI) data bus network. (Refer to ELECTRICAL / 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 the Check Gauges indicator to provide a distinct visual indication of a problem to the vehicle operator. The instrument cluster circuitry may also generate a chime tone when it monitors certain conditions or inputs to provide the vehicle operator with an audible alert.

The EMIC circuitry operates on battery current received through the Ignition-Off Draw (JOD) fuse in the Power Distribution Center (PDC) on a non-switched fused B(+) circuit, and on battery current received through a fuse in the fuse block on a fused ignition switch output (Run-Start) circuit. This arrangement allows the EMIC to provide chime service and interior lighting control 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 by a single ground circuit through one of the instrument cluster connectors and take outs of the instrument panel wire harness. This ground circuit receives ground through a single wire take out with an eyelet terminal connector that is secured under a ground screw to the back of the instrument panel structural support near the lower left corner of the instrument panel, just inboard of the left instrument panel end bracket.

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 indicator lamps and positioning the gauge needles at several predetermined locations on the gauge faces in a prescribed sequence. (Refer to ELECTRICAL / 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 ELECTRICAL / 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 in this service information.