1998 DODGE RAM 1500 Overhead

INPUT AND OUTPUT CIRCUITS
HARD WIRED INPUTS
The hard wired inputs to the EMIC include the fol-
lowing:
²Brake Lamp Switch Output
²Driver Cylinder Lock Switch Sense
²Driver Door Ajar Switch Sense
²Driver Door Lock Switch MUX - with
Power Locks
²Fused B(+) - Ignition-Off Draw
²Fused B(+) - Power Lock Feed - with Power
Locks
²Fused Ignition Switch Output (Accessory-
Run)
²Fused Ignition Switch Output (Off-Run-
Start)
²Fused Ignition Switch Output (Run-Start)
²Headlamp Dimmer Switch MUX
²Headlamp Switch MUX
²Horn Relay Control
²Key-In Ignition Switch Sense
²Left Rear Door Ajar Switch Sense
²Panel Lamps Dimmer Switch Signal
²Park Brake Switch Sense
²Passenger Door Ajar Switch Sense
²Passenger Door Lock Switch MUX - with
Power Locks
²Radio Control MUX
²Right Rear Door Ajar Switch Sense
²RKE Supply - with RKE
²Seat Belt Switch Sense
²Transmission Range Sensor MUX - with
Auto Trans
²Turn/Hazard Switch MUX
²Washer/Beam Select Switch MUX
²Wiper Switch MUX
Refer to the appropriate wiring information for
additional details.
HARD WIRED OUTPUTS
The hard wired outputs of the EMIC include the
following:
²Accessory Switch Bank Illumination Driver
²BTSI Driver - with Auto Trans
²Cargo Lamp Driver
²Dome/Overhead Lamp Driver
²Driver Door Unlock Driver - with Power
Locks
²Headlamp Switch Illumination Driver
²Heated Seat Switch Indicator Driver - with
Heated Seats
²Heater-A/C Control Illumination Driver
²Left Door Lock Driver - with Power Locks
²Left Rear Door Unlock Driver - with Power
Locks²Map/Glove Box Lamp Driver
²Radio Illumination Driver
²Right Door Lock Driver - with Power Locks
²Right Door Unlock Driver - with Power
Locks
²Transfer 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:
²Ground - Illumination (2 Circuits)
²Ground - Power Lock - with Power Locks
²Ground - Signal
²Headlamp Switch Return
²Multi-Function Switch Return
²Transmission Range Sensor Return - with
Auto Trans
Refer to the appropriate wiring information for
additional details.
COMMUNICATION
The EMIC has provisions for the following commu-
nication circuits:
²PCI Data Bus
²RKE Program Serial Data - with RKE
²RKE Transmit Serial Data - with RKE
Refer to the appropriate wiring information for
additional details.
DIAGNOSIS AND TESTING - INSTRUMENT
CLUSTER
If all of the instrument cluster gauges and/or indi-
cators are inoperative, refer to PRELIMINARY
DIAGNOSIS. If an individual gauge or Programma-
ble Communications Interface (PCI) data bus mes-
sage-controlled indicator is inoperative, refer to
ACTUATOR TEST. If an individual hard wired indi-
cator is inoperative, refer to the diagnosis and testing
information for that specific indicator.
Refer to the appropriate wiring information. The
wiring information includes wiring diagrams, proper
wire and connector repair procedures, details of wire
harness routing and retention, connector pin-out
information and location views for the various wire
harness connectors, splices and grounds.
8J - 10 INSTRUMENT CLUSTERDR
INSTRUMENT CLUSTER (Continued)

INSTALLATION
(1) Reach through the glove box opening and
behind the glove box lamp and switch mounting
bracket to feed the instrument panel wire harness
connectors out through the hole in the glove box
lamp and switch housing mounting bracket.
(2) Position the glove box lamp and switch unit to
the instrument panel.
(3) Reconnect the instrument panel wire harness
connector to the connector receptacle on the back of
the glove box lamp and switch unit.
(4) Push the glove box lamp and switch unit into
the hole in the mounting bracket on the instrument
panel glove box opening upper reinforcement.
(5) Install the glove box onto the instrument panel.
(Refer to 23 - BODY/INSTRUMENT PANEL/GLOVE
BOX - INSTALLATION) for the procedures.
(6) Close the glove box.
(7) Reconnect the battery negative cable.
READING LAMP
DESCRIPTION
The overhead console in this vehicle is equipped
with two individual reading and courtesy lamps. The
lamp lenses are the only visible components of these
lamps. Each lamp has its own switch, bulb, reflector
and lens within the overhead console.
The overhead console reading and courtesy lamps
are controlled by the instrument cluster which pro-
vides power at all times, regardless of the ignition
switch position. The ground circuit for the lamps is
switched through the integral reading and courtesy
lamp switches or through the door ajar switches.
Each lamp is designed and aimed to provide illumi-
nation that will be directed only to that side of the
vehicle on which the lamp is located.
The reading and courtesy lamp lenses and bulbs
are available for service replacement. The reading
and courtesy lamp switches, bulb holders and wiring
are only available as part of the overhead console
wire harness. If either of the lamp switches or bulb
holders is faulty or damaged, the entire overhead
console wire harness assembly must be replaced.
For service of the reading and courtesy lamp bulbs,
refer to the appropriate wiring information.
OPERATION
All reading and courtesy lamps located in the over-
head console are activated by the door ajar switches
via the instrument cluster. When all of the doors are
closed, these lamps can be individually activated by
depressing the corresponding lens. When any door is
open, depressing the lamp lenses to activate the lamp
switches will not turn the lamps off.The instrument cluster monitors the door ajar
switches. When a door is open the instrument cluster
grounds the low side drivers to turn on the lamps.
Upon closing all doors, the instrument cluster ini-
tiates a 30 second timer. If any of the doors are
opened during the ªtime outº cycle, the instrument
cluster will reset the timer until all doors are closed.
The instrument cluster will faid to off when the doors
are closed and the ignition is turned ON, the time
out expires or the power locks are activated.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Insert a long, narrow, flat-bladed tool between
the curved (outboard) edge of the reading and cour-
tesy lamp lens and the overhead console housing
(Fig. 4).
(3) Gently pry inward and downward against the
lens until the latch tab in the center of the outboard
edge of the reading and courtesy lamp lens is disen-
gaged from the overhead console housing.
(4) Pull firmly on the lens toward the outboard
side of the vehicle to disengage the two pivot tabs on
the inboard edge of the reading and courtesy lamp
lens are disengaged from the overhead console hous-
ing.
(5) Remove the reading and courtesy lamp lens
from the overhead console housing.
Fig. 4 Overhead Console Reading Lamp Bulb
Removal
1 - LENS
2 - FLAT BLADE
3 - CONSOLE
8L - 28 LAMPS/LIGHTING - INTERIORDR
GLOVE BOX LAMP/SWITCH (Continued)

INSTALLATION
(1) Position the reading and courtesy lamp lens
onto the overhead console housing.
(2) Align the two pivot tabs on the inboard edge of
the reading and courtesy lamp lens with the two
pivot holes in the overhead console housing.
(3) Push firmly on the lens toward the inboard
side of the vehicle to insert the two pivot tabs on the
inboard edge of the reading and courtesy lamp lensinto the two pivot holes in the overhead console hous-
ing.
(4) Pivot the lens back up into position and press
upward firmly until the latch tab in the center of the
outboard edge of the reading and courtesy lamp lens
snaps back into the overhead console housing.
(5) Reconnect the battery negative cable.
DRLAMPS/LIGHTING - INTERIOR 8L - 29
READING LAMP (Continued)

MESSAGE SYSTEMS
TABLE OF CONTENTS
page page
OVERHEAD CONSOLE
DESCRIPTION..........................1
OPERATION............................2
DIAGNOSIS AND TESTING - OVERHEAD
CONSOLE............................2
STANDARD PROCEDURE
STANDARD PROCEDURE - READING/
COURTESY LAMP REPLACEMENT.........3
STANDARD PROCEDURE - MODULE LENS
REPLACEMENT.......................3
STANDARD PROCEDURE - MODULE LAMP
REPLACEMENT.......................3
STANDARD PROCEDURE - COMPASS
CALIBRATION.........................3
STANDARD PROCEDURE - COMPASS
DEMAGNETIZING......................4
STANDARD PROCEDURE - COMPASS
VARIATION ADJUSTMENT................5
REMOVAL
OVERHEAD CONSOLE REMOVAL.........6
INSTALLATION..........................6
COMPASS/MINI-TRIP COMPUTER
DESCRIPTION..........................6
OPERATION............................6
DIAGNOSIS AND TESTING - COMPASS
MINI-TRIP COMPUTER..................6
REMOVAL.............................6
INSTALLATION..........................6
ELECTRONIC VEHICLE INFO CENTER
DESCRIPTION..........................7OPERATION............................7
DIAGNOSIS AND TESTING - ELECTRONIC
VEHICLE INFORMATION CENTER.........8
STANDARD PROCEDURE - ELECTRONIC
VEHICLE INFORMATION CENTER
PROGRAMMING.......................8
REMOVAL.............................9
INSTALLATION..........................9
AMBIENT TEMP SENSOR
DESCRIPTION.........................10
OPERATION...........................10
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR...............10
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR CIRCUIT........10
REMOVAL.............................11
INSTALLATION.........................11
UNIVERSAL TRANSMITTER
DESCRIPTION.........................11
OPERATION...........................11
DIAGNOSIS AND TESTING - UNIVERSAL
TRANSMITTER.......................11
STANDARD PROCEDURE
STANDARD PROCEDURE - ERASING
TRANSMITTER CODES.................12
STANDARD PROCEDURE - SETTING
TRANSMITTER CODES.................12
REMOVAL.............................12
OVERHEAD CONSOLE
DESCRIPTION
Two different overhead consoles are available on
DR models. The Electronic Vehicle Information Cen-
ter (EVIC) (Fig. 1) or Compass Mini-Trip Computer
(CMTC). All consoles are equipped with two reading/
courtesy lamps. The overhead console is mounted
with screws and two snap clips to a molded plastic
retainer bracket located above the headliner.
COMPASS DISPLAY
All the available overhead consoles on this model
include Compass information. While in the compass/
temperature mode, the compass will display the
direction in which the vehicle is pointed using the
eight major compass headings (Examples: north is N,
northeast is NE). The self-calibrating compass unit
requires no adjusting in normal use. The only cali-
bration that may prove necessary is to drive the vehi-
cle at 5 to 8 kilometers-per-hour (3 to 5 miles-per-
hour), on level ground in a square shaped pattern.
This will reorient the compass unit to its vehicle.
DRMESSAGE SYSTEMS 8M - 1

The compass unit also will compensate for magne-
tism the body of the vehicle may acquire during nor-
mal use. However, avoid placing anything magnetic
directly on the roof of the vehicle. Magnetic mounts
for an antenna, a repair order hat, or a funeral pro-
cession flag can exceed the compensating ability of
the compass unit if placed on the roof panel. Mag-
netic bit drivers used on the fasteners that hold the
overhead console assembly to the roof header can
also affect compass operation. If the vehicle roof
should become magnetized, the demagnetizing and
calibration procedures found in this section may be
required to restore proper compass operation.
TEMPERATURE DISPLAY
All the available overhead consoles on this model
include Temperature information. The temperature
displays the outside ambient temperature in whole
degrees. The temperature display can be toggled
from Fahrenheit to Celsius by selecting the desired
U.S./Metric option from the customer programmable
features. The displayed temperature is not an instant
reading of conditions, but an average temperature. It
may take the temperature display several minutes to
respond to a major temperature change, such as driv-
ing out of a heated garage into winter temperatures.
When the ignition switch is turned to the Off posi-
tion, the last displayed temperature reading stays in
the electronic control modules, (CMTC, EVIC) mem-
ory. When the ignition switch is turned to the On
position again, the electronic module will display the
memory temperature for one minute; then update the
display to the current average temperature reading
within five minutes.The temperature function is supported by an ambi-
ent temperature sensor. This sensor is mounted out-
side the passenger compartment near the front and
center of the vehicle, and is hard wired to the Front
Control Module (FCM). The FCM sends temperature
status messages to the module over the J1850 PCI
data bus circuit. For more information on the ambi-
ent temperature sensor, refer to Ambient Tempera-
ture Sensor later in this section.
Following are general descriptions of the major
components used in the overhead console. Refer to
Wiring Diagrams for complete circuit schematics.
OPERATION
Refer to the vehicle Owner's Manual for specific
operation of each overhead console and its systems.
DIAGNOSIS AND TESTING - OVERHEAD
CONSOLE
If the problem with the overhead console is an
inaccurate or scrambled display, refer toSELF-DI-
AGNOSTIC TESTlater in this text. If the problem
with the overhead console is incorrect Vacuum Fluo-
rescent Display (VFD) dimming levels, use a DRB
IIItscan tool and the proper Diagnostic Procedures
manual to test for the correct dimming message
inputs being received from the Body Control Module
(BCM) or Front Control Module (FCM) over the
J1850 Programmable Communications Interface
(PCI) data bus circuit. If the problem is a no-display
condition, use the following procedure. For complete
circuit diagrams, refer toOverhead Consolein the
Wiring Diagrams section of the service manual.
(1) Remove the overhead console from the head-
liner (Refer to 8 - ELECTRICAL/OVERHEAD CON-
SOLE - REMOVAL).
(2) Check for battery voltage at the overhead con-
sole electrical connector. Refer to Wiring for connec-
tor information. If OK, go to Step 3. If not OK, Check
for battery voltage at the appropriate B(+) fuse in the
integrated power module, repair the open fused B(+)
circuit as required.
(3) Turn the ignition switch to the On position.
Check the fused ignition switch output circuit(s) at
the overhead console electrical connector. If OK, go to
Step 4. If not OK, repair the open or shorted circuit
as required.
(4) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Check for continuity between the ground circuit cav-
ity of the overhead console electrical connector and a
good ground. There should be continuity. If OK, refer
toSELF-DIAGNOSTIC TESTbelow for further
diagnosis of the electronics module and the J1850
PCI data bus circuit. If not OK, repair the open
ground circuit as required.
Fig. 1 DR OVERHEAD CONSOLE ± EVIC
8M - 2 MESSAGE SYSTEMSDR
OVERHEAD CONSOLE (Continued)

SELF-DIAGNOSTIC TEST
A self-diagnostic test is built-in to the module to
determine that the electronics module is operating
properly, and that all the J1850 PCI data bus mes-
sages are being received for proper operation. To per-
form the self-diagnostic test proceed as follows:
(1) With the ignition switch in the Off position,
simultaneously depress and hold theSTEP and
RESET buttons.
(2) Turn the ignition switch to the On position.
(3) Following completion of the test, the electronics
module will display one of the following messages:
a.Pass Self Test (EVIC only), PASS (CMTC)-
The electronics module is working properly.
b.Failed Self Test (EVIC only), FAIL (CMTC)-
The electronics module has an internal failure. The
electronics module is faulty and must be replaced.
c.Failed J1850 Communication (EVIC only),
BUS (CMTC)- The electronics module is not receiv-
ing proper message input through the J1850 PCI
data bus circuit. This can result from one or more
faulty electronic modules in the vehicle, or from a
faulty PCI data bus. The use of a DRB IIItscan tool
and the proper Diagnostic Procedures manual are
required for further diagnosis.
NOTE: If the compass functions, but accuracy is
suspect, it may be necessary to perform a variation
adjustment. This procedure allows the compass
unit to accommodate variations in the earth's mag-
netic field strength, based on geographic location.
Refer to Compass Variation Adjustment in the Stan-
dard Procedures section of this group.
NOTE: If the compass reading displays dashes, and
only ªCALº appears in the display, demagnetizing
may be necessary to remove excessive residual
magnetic fields from the vehicle. Refer to Compass
Demagnetizing in the Standard Procedures section
of this group.
STANDARD PROCEDURE
STANDARD PROCEDURE - READING/
COURTESY LAMP REPLACEMENT
(1) Open hood, disconnect and isolate the negative
battery cable.
(2) Remove the reading/courtesy lamp lens. Using
a trim stick, gently pry the forward edge of the read-
ing/courtesy lamp lens outward.
(3) Remove the reading/courtesy lamp socket from
the overhead console. Rotate the reading/courtesy
lamp socket one quarter turn counter clockwise.
(4) Remove the lamp and socket assembly.(5) Reverse the above procedure to install.
STANDARD PROCEDURE - MODULE LENS
REPLACEMENT
(1) Remove the overhead console (Refer to 8 -
ELECTRICAL/OVERHEAD CONSOLE -
REMOVAL).
(2) Remove the electronics module from the over-
head console. Refer to the procedure later in this sec-
tion.
(3) Unsnap the lens from the module and replace
lens as necessary.
STANDARD PROCEDURE - MODULE LAMP
REPLACEMENT
(1) Remove the overhead console (Refer to 8 -
ELECTRICAL/OVERHEAD CONSOLE -
REMOVAL).
(2) Using a flat blade screwdriver twist out socket/
lamp (Fig. 2).
(3) Replace lamp(s) as necessary.
STANDARD PROCEDURE - COMPASS
CALIBRATION
CAUTION: Do not place any external magnets, such
as magnetic roof mount antennas, in the vicinity of
the compass. Do not use magnetic tools when ser-
vicing the overhead console.
Fig. 2 Top of Overhead Console
1 - OVERHEAD CONSOLE HOUSING
2 - EVIC/CMTC MODULE
3 - ILLUMINATION LAMPS
4 - MODULE RETAINING SCREWS
DRMESSAGE SYSTEMS 8M - 3
OVERHEAD CONSOLE (Continued)

The electronic compass unit features a self-cali-
brating design, which simplifies the calibration pro-
cedure. This feature automatically updates the
compass calibration while the vehicle is being driven.
This allows the compass unit to compensate for small
changes in the residual magnetism that the vehicle
may acquire during normal use. If the compass read-
ings appear to be erratic or out of calibration, per-
form the following calibration procedure. Also, new
service replacement Electronic Modules (EVIC,
CMTC) must have their compass calibrated using
this procedure. Do not attempt to calibrate the com-
pass near large metal objects such as other vehicles,
large buildings, or bridges; or, near overhead or
underground power lines.
NOTE: Whenever the compass is calibrated manu-
ally, the variance number must also be reset. Refer
to Compass Variation Adjustment in this group.
To calibrate the compass manually proceed as fol-
lows:
(1) Turn the ignition switch to the On position. If
the compass/temperature data is not currently being
displayed, momentarily depress and release the C/T
push button to reach the compass/temperature dis-
play.
(2) Depress the RESET push button and hold the
button down until ªCALº appears in the display. This
takes about ten seconds, and appears about five sec-
onds after ªVAR = XXº is displayed.
(3) Release the RESET push button.
(4) Drive the vehicle on a level surface, away from
large metal objects and power lines, through three or
more complete turns at between five and eight kilo-
meters-per-hour (three and five miles-per-hour) in
not less than 48 seconds. The ªCALº message will
disappear from the display to indicate that the com-
pass is now calibrated.
NOTE: If the ªCALº message remains in the display,
either there is excessive magnetism near the com-
pass, or the unit is faulty. Repeat the calibration
procedure one more time.
NOTE: If the wrong direction is still indicated in the
compass display, the area selected for calibration
may be too close to a strong magnetic field. Repeat
the calibration procedure in another location.STANDARD PROCEDURE - COMPASS
DEMAGNETIZING
A degaussing tool (Special Tool 6029) is used to
demagnetize, or degauss, the overhead console for-
ward mounting screw and the roof panel above the
overhead console. Equivalent units must be rated as
continuous duty for 110/115 volts and 60 Hz. They
must also have a field strength of over 350 gauss at 7
millimeters (0.25 inch) beyond the tip of the probe.
To demagnetize the roof panel and the overhead
console forward mounting screw, proceed as follows:
(1) Be certain that the ignition switch is in the Off
position, before you begin the demagnetizing proce-
dure.
(2) Connect the degaussing tool to an electrical
outlet, while keeping the tool at least 61 centimeters
(2 feet) away from the compass unit.
(3) Slowly approach the head of the overhead con-
sole mounting screw with the degaussing tool con-
nected.
(4) Contact the head of the screw with the plastic
coated tip of the degaussing tool for about two sec-
onds.
(5) With the degaussing tool still energized, slowly
back it away from the screw. When the tip of the tool
is at least 61 centimeters (2 feet) from the screw
head, disconnect the tool.
(6) Place a piece of paper approximately 22 by 28
centimeters (8.5 by 11 inches), oriented on the vehicle
lengthwise from front to rear, on the center line of
the roof at the windshield header (Fig. 3). The pur-
pose of the paper is to protect the roof panel from
scratches, and to define the area to be demagnetized.
(7) Connect the degaussing tool to an electrical
outlet, while keeping the tool at least 61 centimeters
(2 feet) away from the compass unit.
(8) Slowly approach the center line of the roof
panel at the windshield header, with the degaussing
tool connected.
(9) Contact the roof panel with the plastic coated
tip of the degaussing tool. Be sure that the template
is in place to avoid scratching the roof panel. Using a
slow, back-and-forth sweeping motion, and allowing
13 millimeters (0.50 inch) between passes, move the
tool at least 11 centimeters (4 inches) to each side of
the roof center line, and 28 centimeters (11 inches)
back from the windshield header.
(10) With the degaussing tool still energized,
slowly back it away from the roof panel. When the
tip of the tool is at least 61 centimeters (2 feet) from
the roof panel, disconnect the tool.
(11) Calibrate the compass and adjust the compass
variance (Refer to 8 - ELECTRICAL/OVERHEAD
CONSOLE - STANDARD PROCEDURE).
8M - 4 MESSAGE SYSTEMSDR
OVERHEAD CONSOLE (Continued)

STANDARD PROCEDURE - COMPASS
VARIATION ADJUSTMENT
Compass variance, also known as magnetic decli-
nation, is the difference in angle between magnetic
north and true geographic north. In some geographic
locations, the difference between magnetic and geo-
graphic north is great enough to cause the compass
to give false readings. If this problem occurs, the
compass variance setting may need to be changed.
To set the compass variance:
(1) Using the Variance Settings map, find your
geographic location and note the zone number (Fig.
4).
(2) Turn the ignition switch to the On position. If
the compass/temperature data is not currently being
displayed, momentarily depress and release the C/T
push button to reach the compass/temperature dis-
play.
(3) Depress theRESETpush button and hold the
button down until ªVAR = XXº appears in the display.
This takes about five seconds.
(4) Release theRESETpush button. ªVAR =XX º
will remain in the display. ªXXº equals the current
variance zone setting.
(5) Depress and release theSTEPpush button to
step through the zone numbers, until the zone num-
ber for your geographic location appears in the dis-
play.
Fig. 4 Variance Settings
Fig. 3 Roof Demagnetizing Pattern
DRMESSAGE SYSTEMS 8M - 5
OVERHEAD CONSOLE (Continued)