Part 2 of 2
ALLDATA EDITORS NOTE
The Instrument Panel Gauges and Warning Indicators are not controlled by individual circuits. The ElectroMechanical Instrument Cluster (EMIC) assembly is driven by the BCM via the Programmable Communications Interface (PCI) data bus.
For diagnosis of the EMIC/MIC, Testing and Inspection
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 DRBIII scan tool. Refer to the appropriate diagnostic information. Specific operation details for each gauge may be found elsewhere in this service information.
VACUUM-FLUORESCENT DISPLAYS
The Vacuum-Fluorescent Display (VFD) units are soldered to the EMIC electronic 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) and 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 various diagnostic information when certain fault 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 EMIC microprocessor remembers which display mode is active when the ignition switch is turned to the Off position, and returns the VFD display to that mode when the ignition switch is turned On again.
The VFD units 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 electronic 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, 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.
INDICATORS
Indicators are located in various positions within the EMIC and are all connected to the EMIC electronic 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 diesel engine only Engine Control Module (ECM), 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, 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. 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 DRBIII 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 EMIC circuitry and PCI bus message controlled 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 requires the use of a DRBIII 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 converts 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 into 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 DRBIII 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 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.