Part 2 of 2
GaugesAll 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. 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.
Vacuum-Fluorescent Display
The Vacuum-Fluorescent Display (VFD) module is soldered to the EMIC electronic circuit board. The display is active when either door is opened or with the ignition switch in the ON or Start positions, and inactive about 20 seconds after both doors are closed when the ignition switch is in any other position. If a door is left open with ignition switch in any position except ON or Start, the VFD will remain illuminated until the interior lights control battery saver (load shedding) timer expires after about 20 minutes. The VFD has several display capabilities including: odometer, trip odometer, software version display and can display various diagnostic information. 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 knob that extends through the lower edge of the cluster lens, just right of center. Actuating this switch momentarily with the VFD illuminated will toggle the display between the odometer and trip odometer modes. Depressing the switch button for about 2 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. When illuminated, the VFD will automatically display the message "NO BUS" in place of the odometer or trip odometer information if there is a loss of PCI data bus communication, and will display the message "NO FUSE" if the instrument cluster is not receiving battery current through the fused B(+) circuit from the Ignition-Off Draw (IOD) fuse. The VFD will also display various information used in several diagnostic procedures. Refer to the appropriate diagnostic information for additional details on these VFD functions.
The VFD is diagnosed using the EMIC self-diagnostic actuator test. 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 DRBIII scan tool. Refer to the appropriate diagnostic information. Specific operation details for the odometer and trip odometer functions of the VFD 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 electronic circuit board. The antilock brake system indicator, four-wheel drive indicators, headlamp high beam indicator, front/rear fog lamp indicator, and turn signal indicators are hard wired. The brake indicator is controlled by the hard wired park brake/ brake warning indicator switch input to the EMIC and the EMIC programming. The seatbelt indicator is controlled by the hard wired seat belt switch input to the EMIC and the EMIC programming. 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 display the message "no BuS" in the odometer VFD until PCI data bus communication is restored. The EMIC uses PCI data bus messages from the PCM, Airbag Control Module (ACM), and the Sentry Key Immobilizer Module (SKIM) to control all of the remaining indicators. Different indicators are controlled by different strategies; some receive fused ignition switch output from the EMIC circuitry 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 these indicators to be automatically enabled or disabled by the EMIC circuitry for compatibility with certain optional equipment. The airbag indicator, cruise indicator, and the Sentry Key Immobilizer System (SKIS) indicator are automatically configured. Once a configurable indicator is enabled by the EMIC, it is learned and stored in cluster memory for the remainder of the cluster life.
The hard wired indicators are diagnosed using conventional diagnostic methods. The EMIC and PCI bus message controlled indicators are diagnosed using the EMIC self-diagnostic actuator test. Proper testing of the PCI data bus and the data bus message inputs to the EMIC that control each indicator requires the use of a DRBIII scan tool. Refer to the appropriate diagnostic information. Specific operation details 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 circuitry of the left multi-function switch. The illumination brightness of these lamps is adjusted by the panel lamps dimmer rheostat when the control ring on the left multi-function switch control stalk is rotated (downward to dim, upward to brighten). An analog/digital (A/D) converter in the EMIC converts the analog panel lamps dimmer rheostat input from the left multi-function switch to a digital dimming level pulse-width modulated signal for controlling the lighting levels of the EMIC VFD and cluster illumination lamps. The EMIC also controls and synchronizes the radio and other instrument panel lighting levels through a hard wired panel lamp feed output circuit.
The hard wired cluster illumination inputs and outputs are diagnosed using conventional diagnostic methods. Proper testing of the VFD dimming level and the EMIC A/D converter function require the use of a DRBIII scan tool. Refer to the appropriate diagnostic information.
Chime Service
The EMIC is equipped with hardware and software to provide chime service for all available features in the chime warning system. Upon receiving the proper chime inputs, the EMIC activates an integral chime tone generator to provide the audible chime tone to the vehicle operator. The chime tone generator in the EMIC is capable of producing single chime tones or repeated chime tones at two different rates: a slow rate of about 50 chime tones per minute, and a fast rate of about 180 chime tones per minute. The internal programming of the EMIC determines the priority of each chime tone request input that is received, as well as the rate and duration of each chime tone that is to be generated.
The EMIC relies upon hard wired inputs from the door ajar switches, the left multi-function switch, the ignition switch, and the park brake/brake warning indicator switches to provide chime service for the driver/passenger door ajar warning, the head/park lights-on reminder, and the key-in ignition reminder. For the remaining chime warning functions the EMIC uses a combination of hard wired inputs, electronic message inputs received from other modules over the PCI data bus, and internal programming. (Refer to CHIME/BUZZER - OPERATION). The hard wired chime inputs to the EMIC are diagnosed using conventional diagnostic methods. Proper testing of the EMIC, its programming, and the PCI data bus chime request message functions requires the use of a DRBIII scan tool. Refer to the appropriate diagnostic information.
Interior Lighting Control
The EMIC contains an integral timer and logic circuit to perform both timer and control functions for the interior courtesy lamps. The EMIC uses hard wired inputs from the ignition switch, both door ajar switches on separate driver and passenger door ajar switch sense circuits, from the resistor multiplexed panel lamps dimmer circuitry of the left multi-function switch on the panel lamps dimmer signal circuit and its control logic to provide a battery current output to the courtesy lamps on a courtesy lamp feed circuit. The EMIC control provides a theater-type fade-to-off feature that will slowly dim the courtesy lamps about 5 seconds after both doors are closed. The EMIC also provides an illuminated entry/exit feature by monitoring the door ajar and ignition switch inputs. When a door is opened with the ignition switch in the OFF position, the EMIC turns on the courtesy lamps. When the ignition switch is turned to the ON or Start positions, the EMIC turns the courtesy lamps OFF immediately with no theater dimming. When the ignition switch is turned from the ON position to the OFF position, the EMIC turns on the interior lights for about 10 seconds or until the ignition switch is again turned to the ON or Start positions, whichever occurs first. The EMIC also provides a battery saver feature (load shedding) for the interior lighting. Unless the engine is running, the instrument cluster will automatically turn OFF the interior lights if they are left on for more than about 20 minutes, regardless of the status of the ignition switch, door ajar switch, or left multi-function switch inputs to the cluster.
The hard wired inputs and output of the EMIC interior lighting control can be diagnosed using conventional diagnostic methods; however, there are no other diagnostic tools available for the EMIC timer and logic circuitry. If the input and output components and circuits of the interior lighting system test OK, but the system fails to operate, the EMIC must be replaced.
Rear Window Defogger Control
The EMIC contains an integral timer and logic circuit to perform the rear window defogger timer and control functions for the optional rear window defogger system. The EMIC uses a hard wired input from the rear window defogger switch on the rear window defogger switch sense circuit and its control logic to determine the correct output to the rear window defogger relay. The EMIC controls the ground path of the rear window defogger relay control coil through an output on the rear window defogger relay control circuit. The EMIC is programmed to interpret each momentary ground signal it receives on the rear window defogger switch sense circuit as a request to change the current state of the output on the rear window defogger relay control circuit. Therefore, with the ignition switch in the ON position, the first ground input on the rear window defogger switch sense circuit turns the system ON, the second ground input turns the system OFF, and so forth. Once the rear window defogger system has been turned ON, it can be turned OFF manually by depressing the rear window defogger switch a second time or by turning the ignition switch to the OFF position. The timer function of the EMIC will also automatically turn the rear window defogger system OFF. The timer turns the system OFF after about 10 minutes of operation; however, after the first timed interval has expired, each time the system is turned ON again during that same ignition cycle, the timer will automatically turn it OFF after about 5 minutes of operation.
The hard wired input and output of the EMIC rear window defogger control can be diagnosed using conventional diagnostic methods; however, there are no other diagnostic tools available for the EMIC rear window defogger timer and logic circuitry. If the input and output components and circuits of the rear window defogger system test OK, but the system fails to operate, the EMIC must be replaced.