Dodge Ram Truck 1500-2500-3500. Manual — part 386

OPERATION

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 com-
ponent 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 stan-
dard 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 mes-
sages that are transmitted by other electronic modules over the Programmable Communications Interface (PCI) data
bus. (Refer to 8 - ELECTRICAL/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 transducer to provide distinct visual and audible indications of
a problem to the vehicle operator. The EMIC 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 on a non-switched fused B(+)
circuit, and on battery current received through a fused ignition switch output (run-start) fuse on a fused ignition
switch output (run-start) circuit. This arrangement allows the EMIC to provide some features regardless of the igni-
tion 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 by a ground screw to a ground location near the center of 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 predeter-
mined 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 8 - ELECTRICAL/INSTRUMENT CLUS-
TER - DIAGNOSIS AND TESTING).

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 8 - 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 each gauge require the use of a diagnostic scan tool. Refer to the appropriate diag-
nostic information. Specific operation details for each gauge may be found elsewhere in this service information.

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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 posi-
tions.

The illumination intensity of the VFD units is controlled by the EMIC circuitry based upon an input from the head-
lamp switch and a dimming level input received from the panel dimmer switch. The EMIC synchronizes the illumi-
nation 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 (except SRT-
10), gear selector indication (PRNDL) for models with an automatic transmission, several warning or reminder indi-
cations, 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 depress-
ing 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 the
odometer/trip odometer switch for about six seconds will display the engine hours information. The engine hours
feature is disabled for SRT-10 models. 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 instrument cluster diag-
nosis and testing service information for additional details on this cluster function. The EMIC microprocessor remem-
bers 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 8 - ELECTRICAL/INSTRU-
MENT 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 diagnostic 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 else-
where 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 con-
trolled 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. The tow/haul indicator and those located within the VFD units are
dimmable. All other indicators are illuminated at a fixed intensity, which is not affected by the selected illumination
intensity of the EMIC general illumination lamps. The illumination intensity of the dimmable indicators is synchro-
nized with that 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 equip-
ment. 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 diagnostic scan tool for vehicles that do not have this equip-
ment. 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.

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The hard wired indicator inputs may be diagnosed using conventional diagnostic methods. However, the EMIC cir-
cuitry and PCI bus message controlled indicators are diagnosed using the EMIC self-diagnostic actuator test. (Refer
to 8 - ELECTRICAL/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 diagnostic 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 whenever the exterior lighting is turned On. The illu-
mination 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 fused 12-volt input it receives 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 control the illumination intensity of 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 illu-
mination lamps in the vehicle. The EMIC also transmits 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 or funeral
mode. The EMIC monitors the request for this mode from the headlamp switch, then transmits an electronic dim-
ming level message 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 panel lamps dimmer inputs to and outputs from the EMIC may be diagnosed
using conventional diagnostic methods. However, proper testing of the PWM processing of the EMIC and the elec-
tronic dimming level messages sent by the EMIC over the PCI data bus 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:

•

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

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•

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

•

Oil Temperature Gauge Illumination Driver - SRT-10 only

•

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.

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