Part 2

Fig. 3 Gauges & Indicators - Gasoline Engine:

The EMIC houses six analog gauges and has provisions for up to twenty-three indicators (Fig. 3). The EMIC includes the following 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 (Fig.3):
- Airbag Indicator (with Airbag System only)
- Antilock Brake System (ABS) Indicator (with ABS or Rear Wheel Anti-Lock [RWAL] brakes only)
- Brake Indicator
- Cargo Lamp Indicator
- Check Gauges Indicator
- Cruise Indicator (with Speed Control only)
- Door Ajar Indicator
- Gear Selector Indicator (with Automatic Transmission only)
- High Beam Indicator
- Lamp Out Indicator
- Low Fuel Indicator
- Malfunction Indicator Lamp (MIL)
- Overdrive-Off Indicator (with Automatic Transmission only)
- Seatbelt Indicator
- Security Indicator (with Sentry Key Immobilizer & 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

Each indicator in the EMIC, except those located within one of the VFD units, is illuminated by a dedicated Light Emitting Diode (LED) that is soldered onto the EMIC electronic circuit board. The LEDs are not available for service replacement and, if damaged or faulty, the entire EMIC must be replaced. Cluster illumination is accomplished by dimmable incandescent back lighting, which illuminates the gauges for visibility when the exterior lighting is turned on. Each of the incandescent bulbs is secured by an integral bulb holder to the electronic circuit board from the back of the cluster housing. The incandescent bulb/bulb holder units are available for service replacement.

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, hood and mask unit and the individual incandescent lamp bulbs with holders are available for service replacement.

The Electromechanical Instrument Cluster (EMIC) in this model also includes the hardware and software necessary to serve as the electronic body control module and is sometimes 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 EMIC controls. For example:

Additional details of the audible warning functions of the EMIC are found within the Chime/Buzzer service information.

The 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 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 generator to provide distinct visual and audible indications of a problem to the vehicle operator. The instrument cluster circuitry may also produce audible warnings for other electronic modules in the vehicle based upon electronic tone request messages received over the PCI data bus. Each audible warning is intended to provide the vehicle operator with an audible alert to supplement a visual indication.

The EMIC circuitry operates on battery current received through a fused B(+) fuse in the Integrated Power Module (IPM) on a non-switched fused B(+) circuit, and on battery current received through a fused ignition switch output (run-start) fuse in the IPM 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 a ground circuit and take out of the instrument panel wire harness with an eyelet terminal connector that is secured to a ground location on the instrument panel structural support.

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 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.

Vacuum-Fluorescent Displays
The Vacuum-Fluorescent Display (VFD) units are soldered to the EMIC circuit board. With the ignition switch in the OFF or Accessory positions, the odometer display is activated when the driver door is opened (Rental Car mode) is deactivated when the driver door is closed. Otherwise, both display 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 EMIC circuitry based upon an input from the headlamp switch and a dimming level input received from the headlamp dimmer switch. The EMIC synchronizes the illumination intensity of other VFD units with that of the units in the EMIC by sending electronic dimming level messages to other electronic modules in the vehicle over the PCI data bus.

The EMIC VFD units have several display capabilities including odometer, trip odometer, engine hours, gear selector indication (PRNDL) for models with an automatic transmission, several warning or reminder indications, and certain diagnostic information whenever the appropriate conditions exist. An odometer/ trip odometer switch on the EMIC circuit board is used to control some 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 the tachometer. Actuating this switch momentarily with the ignition switch in the ON position will toggle the VFD between the odometer and trip odometer modes. 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. While in the odometer mode with the ignition switch in the ON position and the engine not running, depressing this switch for about six seconds will display the engine hours information. Holding this switch depressed while turning the ignition switch from the OFF position to the ON position will initiate the EMIC self-diagnostic actuator test. Refer to the appropriate diagnostic information for additional details on this VFD function.

The VFD is diagnosed using the EMIC self-diagnostic actuator test. (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). Proper testing of the PCI data bus and the electronic 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, the trip odometer, the gear selector indicator and the various warning and reminder indicator functions of the VFD may be found elsewhere in this service information.

Gauges
All gauges receive battery current through the EMIC circuitry only 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 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 electronic 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.

Indicators
Indicators are located in various positions within the EMIC and are all connected to the EMIC circuit board. The cargo lamp indicator, door ajar indicator, high beam indicator, and turn signal indicators operate based upon hard wired inputs to the EMIC. The brake indicator is controlled by PCI data bus messages from the Controller Antilock Brake (CAB) as well as by hard wired park brake switch inputs to the EMIC. The seatbelt indicator is controlled by the EMIC programming, PCI data bus messages from the Airbag Control Module (ACM), and a hard wired seat belt switch input to the EMIC. 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 communication, the EMIC circuitry will automatically turn the MIL on until PCI data bus communication is restored. The EMIC uses PCI data bus messages from the Front Control Module (FCM), the PCM, the ACM, the CAB, and the Sentry Key Immobilizer Module (SKIM) to control all of the remaining indicators.

The various EMIC indicators are controlled by different strategies; some receive fused ignition switch output from the EMIC circuitry and have a switched ground, others are grounded through the EMIC circuitry and have a switched battery feed. However, all indicators are completely controlled by the EMIC microprocessor based upon various hard wired and electronic message inputs. All indicators are illuminated at a fixed intensity, which is not affected by the selected illumination intensity of the EMIC general illumination lamps.

In addition, certain indicators in this instrument cluster are automatically configured or self-configured. This feature allows the configurable indicators to be enabled by the EMIC circuitry for compatibility with certain optional equipment. The EMIC defaults for the ABS indicator and airbag indicator are enabled, and these configuration settings must be programmatically disabled in the EMIC using a DRB III scan tool for vehicles that do not have this equipment. The automatically configured or self-configured indicators remain latent in each EMIC at all times and will be active only when the EMIC receives the appropriate PCI message inputs for that optional system or equipment.

The hard wired indicator inputs may be diagnosed using conventional diagnostic methods. However, the indicators and the EMIC circuitry and PCI data bus electronic messages that control the indicators 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 electronic message inputs to the EMIC that control an indicator require the use of a DRB III scan tool. Refer to the appropriate diagnostic information. Specific details of the operation for each indicator may be found elsewhere in this service information.

Cluster Illumination
The EMIC has several illumination lamps that are illuminated when the exterior lighting is turned on with the headlamp switch. The illumination intensity of these lamps is adjusted when the interior lighting thumbwheel on the headlamp switch is rotated (down to dim, up to brighten) to one of six available minor detent positions. The EMIC monitors a resistor multiplexed input from the headlamp switch on a dimmer input circuit. In response to that input, the EMIC electronic circuitry by converting a 12-volt input it receives from a fuse in the Integrated Power Module (IPM) on a hard wired panel lamps dimmer switch signal circuit to a 12-volt Pulse Width Modulated (PWM) output. The EMIC uses this PWM output to power the cluster illumination lamps and the VFD units on the EMIC circuit board, then provides a synchronized PWM output on the 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 cluster illumination lamps are grounded at all times.

The EMIC also sends electronic dimming level messages over the PCI data bus to other electronic modules in the vehicle to control and synchronize the illumination intensity of their VFD units to that of the EMIC VFD units. In addition, the thumbwheel on the headlamp switch has a Parade Mode position to provide a parade mode. The EMIC monitors the request for this mode from the headlamp switch, then sends an electronic dimming level message over the PCI data bus to illuminate all VFD units in the vehicle at full (daytime) intensity for easier visibility when driving in daylight with the exterior lighting turned on.

The hard wired headlamp switch and EMIC panel lamps dimmer inputs and outputs may be diagnosed using conventional diagnostic methods. However, proper testing of the PWM output of the EMIC and the electronic dimming level messages sent by the EMIC over the PCI data bus requires the use of a DRB III scan tool. Refer to the appropriate diagnostic information.

INPUT AND OUTPUT CIRCUITS

Hard Wired Inputs
The hard wired inputs to the EMIC include the following:
- Brake Lamp Switch Output
- Driver Cylinder Lock Switch Sense
- Driver Door Ajar Switch Sense
- Driver Door Lock Switch MUX - with Power Locks
- Fused B(+) - Ignition-Off Draw
- Fused B(+) - Power Lock Feed - with Power Locks
- Fused Ignition Switch Output (Accessory-Run)
- Fused Ignition Switch Output (Off-Run-Start)
- Fused Ignition Switch Output (Run-Start)
- Headlamp Dimmer Switch MUX
- Headlamp Switch MUX
- Horn Relay Control
- Key-In Ignition Switch Sense
- Left Rear Door Ajar Switch Sense
- Panel Lamps Dimmer Switch Signal
- Park Brake Switch Sense
- Passenger Cylinder Lock Switch Sense
- Passenger Door Ajar Switch Sense
- Passenger Door Lock Switch MUX - with Power Locks
- Radio Control MUX
- Right Rear Door Ajar Switch Sense
- RKE Supply - with RKE
- Seat Belt Switch Sense
- Transmission Range Sensor MUX - with Auto Trans
- Turn/Hazard Switch MUX
- Washer/Beam Select Switch MUX
- Wiper Switch MUX

Refer to the appropriate wiring information for additional details.

Hard Wired Outputs
The hard wired outputs of the EMIC include the following:
- Accessory Switch Bank Illumination Driver
- BTSI Driver - with Auto Trans
- Cargo Lamp Driver
- Dome/Overhead Lamp Driver
- Driver Door Unlock Driver - with Power Locks
- Headlamp Switch Illumination Driver
- Heated Seat Switch Indicator Driver - with Heated Seats
- Heater-A/C Control Illumination Driver
- Left Door Lock Driver - with Power Locks
- Left Rear Door Unlock Driver - with Power Locks
- Map/Glove Box Lamp Driver
- Radio Illumination Driver
- Right Door Lock Driver - with Power Locks
- Right Door Unlock Driver - with Power Locks
- Transfer Case Switch Illumination Driver - with Four-Wheel Drive
Refer to the appropriate wiring information for additional details.

Grounds
The EMIC receives and supplies a ground path to several switches and sensors through the following hard wired circuits:
- Ground - Illumination (2 Circuits)
- Ground - Power Lock - with Power Locks
- Ground - Signal
- Headlamp Switch Return
- Multi-Function Switch Return
- Transmission Range Sensor Return - with Auto Trans

Refer to the appropriate wiring information for additional details.

Communication
The EMIC has provisions for the following communication circuits:
- PCI Data Bus
- RKE Program Serial Data - with RKE
- RKE Transmit Serial Data - with RKE

Refer to the appropriate wiring information for additional details.