Instrument Cluster Description
INSTRUMENT CLUSTERFig.1 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 remainder of the EMIC, including the mounts and the electrical connections, are concealed within the instrument panel behind the cluster bezel. Besides analog gauges and indicators, the EMIC module incorporates one or two blue-green digital Vacuum Fluorescent Display (VFD) units for displaying odometer/trip odometer information, automatic transmission gear selector position (PRNDL), several warning or reminder indications and certain diagnostic information.
Fig.2 Instrument Cluster Components:
The EMIC gauges and indicators are visible through a dedicated opening in the cluster bezel on the instrument panel and are protected by a clear plastic cluster lens (Fig. 2). Just behind the cluster lens is the cluster hood and mask unit, which is 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. A black plastic odometer/trip odometer switch button protrudes through dedicated holes in the cluster mask and the cluster lens, located near the lower edge of the cluster just to the left of center. The molded plastic EMIC lens, and the hood and mask unit have seven integral mounting tabs, three along the upper edge and four along the lower edge. These mounting tabs are used to secure the lens, hood and mask to the molded plastic cluster housing with seven screws.
The rear of the cluster housing and the EMIC electronic circuitry are protected by a fiberboard rear cover, which is secured to the cluster housing with six screws. The rear cover includes clearance holes for service access to each of the incandescent bulb and bulb holder units installed on the cluster circuit board for general illumination lighting and some indicators, as well as cutouts for the two cluster connector receptacles. The connector receptacles on the back of the cluster electronic circuit board connect the EMIC to the vehicle electrical system through two take outs from the instrument panel wire harness, each equipped with a self-docking connector. 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.
Sandwiched between the rear cover and the lens, hood and mask unit is the cluster housing. The molded plastic cluster housing serves as the carrier for the cluster circuit board and circuitry, the cluster connector receptacles, the gauges, numerous Light Emitting Diode (LED) units for cluster indicators, one or two Vacuum Fluorescent Display (VFD) units, the cluster overlay, the gauge pointers, the odometer/trip odometer switch and the switch button. 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 various LED units and incandescent lamps behind it to be visible through the outer layer of the overlay only through predetermined cutouts. A rectangular opening in the lower edge of the overlay near the left outboard end of the cluster has a smoked clear lens through which the illuminated odometer/trip odometer VFD unit can be viewed. Models equipped with an automatic transmission have a second opening near the right outboard end of the cluster for the gear selector indicator VFD unit.
Several versions of the EMIC module are offered on this model. These versions accommodate all of the variations of optional equipment and regulatory requirements for the various markets in which the vehicle will be offered. The microprocessor-based EMIC utilizes integrated circuitry and information carried on the Programmable Communications Interface (PCI) data bus network along with several hard wired analog and multiplexed inputs to monitor sensor and switch inputs throughout the vehicle. In response to those inputs, the internal circuitry and programming of the EMIC 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 PCI data bus. (Refer to COMMUNICATION - DESCRIPTION - PCI BUS). Besides typical instrument cluster gauge and indicator support, the electronic functions and features that the EMIC supports or controls include the following:
- Brake Transmission Shift Interlock Control - On models with an automatic transmission, the EMIC monitors inputs from the ignition switch and either the Transmission Range Sensor (TRS) or electronic gear selector indicator messages received from the Transmission Control Module over the PCI data bus, then controls a high-side driver output to operate the Brake Transmission Shift Interlock (BTSI) solenoid. The BTSI locks the automatic transmission gearshift selector lever on the steering column in the Park position when the brake pedal is released. The BTSI solenoid is de-energized to unlock the gear selector lever from the Park position only when the brake pedal is depressed.
- 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 Synchronization - The EMIC transmits electronic panel lamp dimming level messages which allows modules with Vacuum Fluorescent Displays VFD) to coordinate their illumination intensity with that of the EMIC VFD units.
The EMIC houses both analog gauges and indicators. The EMIC includes the following six analog gauges:
- Coolant Temperature Gauge
- Fuel Gauge
- Oil Pressure Gauge
- Speedometer
- Tachometer
- Voltage Gauge
Some of the EMIC indicators are automatically configured when the EMIC is connected to the vehicle electrical system for compatibility with certain optional equipment or equipment required for regulatory purposes in certain markets. While each EMIC may have provisions for indicators to support every available option, the configurable indicators will not be functional in a vehicle that does not have the equipment that an indicator supports. The EMIC includes provisions for the following indicators:
- Airbag Indicator
- Antilock Brake System (ABS) Indicator
- Brake Indicator
- Cargo Lamp Indicator
- Check Gauges Indicator
- Cruise Indicator (Odometer VFD)
- Door Ajar Indicator
- Gear Selector Indicator (with Automatic Transmission only)
- High Beam Indicator
- Low Fuel Indicator
- Malfunction Indicator Lamp (MIL)
- Overdrive-Off Indicator (with Automatic Transmission Only)
- Seatbelt Indicator
- Security Indicator (with Sentry Key Immobilizer or Vehicle Theft Security Systems only)
- Service Four-Wheel Drive Indicator (with Four-Wheel Drive only)
- Transmission Overtemp Indicator (with Automatic Transmission only)
- Turn Signal (Right and Left) Indicators
- Upshift Indicator (with Manual Transmission only)
- Washer Fluid Indicator
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) unit 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, a VFD unit, 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, and the individual incandescent lamp bulbs with holders are available for 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 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 high coolant temperature, the algorithm can drive the gauge pointer to an extreme position and the microprocessor can turn ON a "Check Gauges" indicator and generate an electronic chime tone request message to the Central Timer Module (CTM) over the PCI data bus to sound an audible chime to provide distinct visual and audible indications of a problem to the vehicle operator.
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, positioning the gauge needles at several predetermined calibration points across the gauge faces, and illuminating all segments of the odometer/trip odometer and the automatic transmission gear selector indicator Vacuum-Fluorescent Display (VFD) units. (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.