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, elec-
tronic message inputs received from other modules
over the PCI data bus, and internal programming.
(Refer
to
8
-
ELECTRICAL/CHIME/BUZZER
-
OPERATION).
The hard wired chime inputs to the EMIC may be
diagnosed using conventional diagnostic methods.
However, proper testing of the EMIC programming
and the electronic chime request messages received
by the EMIC over the PCI data bus requires the use
of a DRBIII
t scan tool. Refer to the appropriate diag-
nostic information.
ELECTRONIC PINION FACTOR
Each time the EMIC receives an electronic pinion
factor request message from the Powertrain Control
Module (PCM) over the PCI data bus, it provides a
response to the PCM containing the appropriate elec-
tronic pinion factor information. Because there are
numerous optional combinations of tire size, axle
ratio, and transfer case type which are available for
this vehicle, the electronic pinion factor needs to be
considered for accurate processing of the vehicle
speed and distance information. The instrument clus-
ter stores the electronic pinion factor information and
broadcasts it over the PCI data bus upon request by
the PCM. Using this factor and the Vehicle Speed
Sensor (VSS) input, the PCM then calculates the
proper vehicle speed and distance information, and
transmits the appropriate electronic vehicle speed
messages over the PCI data bus for use by other elec-
tronic modules in the vehicle.
Proper testing of the PCI data bus and the elec-
tronic data bus message inputs to and outputs from
the EMIC that control the electronic pinion factor
function requires the use of a DRBIII
t scan tool.
Refer to the appropriate diagnostic information.
INTERIOR LIGHTING CONTROL
The EMIC contains an integral timer and logic cir-
cuit 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-func-
tion switch on the panel lamps dimmer signal circuit
and its control logic to provide a battery current out-
put 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 five seconds after both doors are closed.
The EMIC interior lighting control programming
provides an illuminated entry/exit feature by moni-
toring 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 ten seconds or until the ignition switch is
again turned to the On or Start positions, whichever
occurs first.
The EMIC interior lighting control programming
also provides a battery saver feature (load shedding)
for the interior lighting. Unless the engine is run-
ning, the EMIC will automatically turn off the inte-
rior lights if they are left on for more than about
twenty minutes, regardless of the status of the igni-
tion 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 may be diagnosed using con-
ventional diagnostic methods; however, there are no
other diagnostic tools available for the EMIC timer
and logic circuitry. If the input and output compo-
nents and circuits of the interior lighting system test
OK, but the system fails to operate as designed, the
EMIC must be replaced.
REAR WINDOW DEFOGGER CONTROL
The EMIC contains an integral timer and logic cir-
cuit to perform the rear window defogger timer and
control functions for the optional rear window defog-
ger 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 win-
dow 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.
TJ
INSTRUMENT CLUSTER
8J - 9
INSTRUMENT CLUSTER (Continued)