Part 2

Except for the indications provided within the multi-function indicator LCD unit, each indicator in the EMIC is illuminated by a dedicated LED that is soldered onto the EMIC electronic circuit board. Cluster illumination is accomplished by dimmable LED back lighting, which illuminates the gauges for visibility when the exterior lighting is turned on. The cluster general illumination LED units are also soldered onto the EMIC electronic circuit board. The LED units are not available for service replacement and, if damaged or faulty, the entire EMIC must be replaced.

Hard wired circuitry connects the EMIC to the electrical system of the vehicle. These hard wired circuits are integral to the vehicle 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 multifunction indicator LCD unit, an electronic tone generator, the electronic circuit board, the circuit board hardware, the cluster overlay, the cluster housing, the cluster hood, the cluster lens, or the cluster rear cover are damaged or faulty, the entire EMIC module must be replaced.

OPERATION
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, meters and indicators in the EMIC provide valuable information about the powertrain, fuel and emissions systems, cooling system, 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 many are in the form of electronic messages that are transmitted by other electronic modules over the Controller Area Network (CAN) data bus network.

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 also provides audible turn signal and hazard warning support by emulating the "ticking" sound associated with a conventional electro-mechanical flasher using a contactless relay. The relay will also provide an indication of a turn signal failure by sounding at double the usual frequency. Each audible warning is provided to the vehicle operator to supplement a visual indication.

The EMIC circuitry operates on battery current received through a non-switched fused B(+) circuit, and on a fused ignition switch output circuit. The EMIC circuitry is grounded through a ground circuit and take out of the frame wire harness with an eyelet terminal connector that is secured to a stud by a nut at a ground location on the dash panel just forward of the instrument cluster. Separate switched ground inputs from the key-in ignition switch and the front door jamb switches provide wake-up signals to the EMIC circuitry. 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 position.

Proper diagnosis and testing of the EMIC, the CAN data bus, the data bus electronic message inputs to and outputs from the EMIC, as well as the retrieval or erasure of a Diagnostic Trouble Code (DTC) requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information. 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 only when the instrument cluster detects the ignition switch is in the On position. 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 position.

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 CAN data bus. The gauge needle moves as the movable permanent magnet aligns itself to the changing magnetic fields created around it by the electromagnets.

Proper diagnosis and testing of the gauges, the CAN data bus and the electronic data bus message inputs to the EMIC that control each gauge require the use of a diagnostic scan tool.

INDICATORS
Indicators are located in various positions within the EMIC and are all connected to the EMIC electronic circuit board. The ambient temperature indicator (optional), brake indicator, brake wear indicator, charging indicator, coolant low indicator, high beam indicator, low fuel indicator, park brake indicator, seatbelt indicator, turn signal indicators, and washer fluid indicator operate based upon hard wired inputs to the EMIC. The airbag (SRS) indicator is normally controlled by a hard wired input from the Airbag Control Module (ACM); however, if the EMIC sees an abnormal or no input from the ACM, it will automatically turn the airbag indicator On until the hard wired input from the ACM has been restored. The Malfunction Indicator Lamp (MIL) is normally controlled by CAN data bus messages from the Engine Control Module (ECM); however, if the EMIC loses CAN data bus communication, the EMIC circuitry will automatically turn the MIL on until CAN data bus communication is restored. The EMIC uses CAN data bus messages from the ECM, the ACM, and the Controller Antilock Brake to control all of the remaining indicators.

The various EMIC indicators are controlled by different strategies; some receive battery feed from the EMIC circuitry and have a switched ground, while 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. Except for the indications provided by the multi-function indicator Liquid Crystal Display (LCD) unit, all indicators are illuminated at a fixed intensity, which is not affected by the selected illumination intensity of the EMIC general illumination lamps.

The hard wired indicator inputs may be diagnosed using conventional diagnostic methods. However, proper testing of the EMIC circuitry and the CAN bus message controlled indicators requires the use of a diagnostic scan tool.

CLUSTER ILLUMINATION
The EMIC has several general illumination lamps that are illuminated when the exterior lighting is turned on with the multi-function switch. The illumination intensity of these lamps is adjusted by a dimming level input received from the multi-function indicator "+" (plus) and "-" (minus) switch push buttons that extend through the lower edge of the cluster lens below the right end of the multi-function indicator. When the exterior lighting is turned Off, the display is illuminated at maximum brightness. When the exterior lighting is turned On and the transmission gear selector is in the Park position, depressing the plus switch push button brightens the display lighting, and depressing the minus switch push button dims the display lighting. The EMIC also provides a Pulse-Width Modulated (PWM) panel lamps dimmer output that can be used to synchronize the illumination lighting levels of external illumination lamps (up to about 23 to 30 watts) with that of the EMIC.

The hard wired multi-function switch input and the EMIC panel lamps dimmer output may be diagnosed using conventional diagnostic methods. However, proper testing of the PWM control of the EMIC and the electronic dimming level inputs from the multi-function indicator push buttons requires the use of a diagnostic 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:

NOTE: Final approved circuit names were not yet available at the time this information was compiled.

- Airbag Indicator Driver
- Ambient Temperature Sensor Signal (Optional)
- Brake Wear Indicator Sense
- Charging Indicator Driver
- Coolant Level Switch Sense
- Front Door Jamb Switch Sense
- Fuel Level Sensor Signal
- Fused B(+)
- Fused Ignition Switch Output
- High Beam Indicator Driver
- Key-In Ignition Switch Sense
- Left Turn Signal
- Park Brake Switch Sense
- Right Turn Signal
- Seat Belt Switch Sense
- Washer Fluid Switch Sense (Optional)

HARD WIRED OUTPUTS
The hard wired outputs of the EMIC include the following:
- Engine Running Relay Control
- Panel Lamps Driver
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:
- Ambient Temperature Sensor Return (Optional)
- Fuel Level Sensor Return
- Ground

COMMUNICATION
The EMIC has provisions for the following communication circuits:
- CAN Data Bus - High
- CAN Data Bus - Low
- Diagnostic Serial Communication Interface (SCI) Data Bus Line.

Refer to the appropriate wiring information for additional details.