• Actuator Test - Each time the cluster is put
through the actuator test, the MIL will be turned on,
then off again during the bulb check portion of the
test to confirm the functionality of the LED and the
cluster control circuitry.
The PCM continually monitors the fuel and emis-
sions system circuits and sensors to decide whether
the system is in good operating condition. The PCM
then sends the proper lamp-on or lamp-off messages
to the instrument cluster. For further diagnosis of
the MIL or the instrument cluster circuitry that con-
trols the LED, (Refer to 8 - ELECTRICAL/INSTRU-
MENT CLUSTER - DIAGNOSIS AND TESTING). If
the instrument cluster turns on the MIL after the
bulb test, it may indicate that a malfunction has
occurred and that the fuel and emissions system may
require service. For proper diagnosis of the fuel and
emissions systems, the PCM, the PCI data bus, or
the electronic message inputs to the instrument clus-
ter that control the MIL, a DRBIII
t scan tool is
required. Refer to the appropriate diagnostic infor-
mation.
ODOMETER
DESCRIPTION
An odometer and trip odometer are standard
equipment in all instrument clusters (Fig. 19). The
odometer and trip odometer information are dis-
played in a common electronic, blue-green Vacuum
Fluorescent Display (VFD). The VFD is soldered onto
the cluster electronic circuit board and is visible
through a window with a smoked clear lens located
near the lower edge of the cluster overlay between
the tachometer and speedometer. The dark lens over
the VFD prevents it from being clearly visible when
it is not illuminated. However, the odometer, and trip
odometer information are not displayed simulta-
neously. The trip odometer reset switch on the
instrument cluster circuit board toggles the display
between odometer and trip odometer modes by
depressing the odometer/trip odometer switch button
that extends through the lower edge of the cluster
lens, just right of the odometer VFD.
The odometer and trip odometer information is
stored in the instrument cluster memory. This infor-
mation can be increased when the proper inputs are
provided to the instrument cluster, but the informa-
tion cannot be decreased. The odometer can display
values up to 999,999 kilometers (999,999 miles). The
odometer latches at these values, and will not roll
over to zero. The trip odometer can display values up
to 9,999.9 kilometers (9,999.9 miles) before it rolls
over to zero. The odometer display does not have a
decimal point and will not show values less than a
full unit (kilometer or mile), while the trip odometer
display does have a decimal point and will show
tenths of a unit (kilometer or mile). The unit of mea-
sure (kilometers or miles) for the odometer and trip
odometer display is not shown in the VFD. The unit
of measure for the instrument cluster odometer/trip
odometer is selected at the time that it is manufac-
tured, and cannot be changed. If the instrument clus-
ter has a speedometer with a primary scale in
kilometers-per-hour, the letters “KM” are printed on
the cluster mask next to the VFD window to indicate
the odometer unit of measure.
The odometer has a “Rental Car” mode, which will
illuminate the odometer information in the VFD
whenever the driver side front door is opened with
the ignition switch in the Off or Accessory positions.
During daylight hours (exterior lamps are Off) the
VFD is illuminated at full brightness for clear visibil-
ity. At night (exterior lamps are On) the VFD lighting
level is adjusted with the other cluster illumination
lamps using the panel lamps dimmer control ring on
the control stalk of the left multi-function switch.
However, a “Parade” mode position of the panel
lamps dimmer control ring allows the VFD to be illu-
minated at full brightness if the exterior lamps are
turned On during daylight hours.
The VFD, the trip odometer switch, and the trip
odometer switch button are serviced as a unit with
the instrument cluster. The rubber trip odometer
reset knob boot that seals the hole in the cluster lens
through which the reset knob protrudes is available
for individual service replacement.
OPERATION
The odometer and trip odometer give an indication
to the vehicle operator of the distance the vehicle has
traveled. This indicator is controlled by the instru-
ment cluster circuitry based upon cluster program-
ming and electronic messages received by the cluster
from the Powertrain Control Module (PCM) over the
Programmable Communications Interface (PCI) data
bus. The odometer and trip odometer information is
displayed by the instrument cluster Vacuum Fluores-
cent Display (VFD). The VFD will display the odom-
eter information whenever the driver door is opened
with the ignition switch in the Off or Accessory posi-
tions, and will display the last previously selected
odometer or trip odometer information when the igni-
tion switch is turned to the On or Start positions.
The instrument cluster circuitry controls the VFD
and provides the following features:
Fig. 19 Odometer Display
TJ
INSTRUMENT CLUSTER
8J - 33
MALFUNCTION INDICATOR LAMP (MIL) (Continued)