Check Gauges Indicator; Description; Operation - Jeep Wrangler 2001 Service Manual

TJ
BRAKE/PARK BRAKE INDICATOR (Continued)
(4) Check for continuity between the terminal of
the park brake switch and a good ground. There
should be no continuity with the park brake released,
and continuity with the park brake applied. If not
OK, replace the faulty park brake switch.

CHECK GAUGES INDICATOR

DESCRIPTION

A check gauges indicator is standard equipment on
all instrument clusters. The check gauges indicator is
located on the lower edge of the instrument cluster
overlay, to the right of the odometer/trip odometer
Vacuum-Fluorescent Display
gauges indicator consists of a stencil-like cutout of
the words "CHECK GAUGES" in the opaque layer of
the instrument cluster overlay. The dark outer layer
of the overlay prevents the indicator from being
clearly visible when it is not illuminated. A red lens
behind the cutout in the opaque layer of the overlay
causes the "CHECK GAUGES" text to appear in red
through the translucent outer layer of the overlay
when the indicator is illuminated from behind by a
Light Emitting Diode (LED) soldered onto the instru-
ment cluster electronic circuit board. The check
gauges indicator is serviced as a unit with the instru-
ment cluster.

OPERATION

The check gauges indicator gives an indication to
the vehicle operator when certain instrument cluster
gauge readings reflect a condition requiring immedi-
ate attention. This indicator is controlled by a tran-
sistor on the instrument cluster electronic circuit
board based upon cluster programming and elec-
tronic messages received by the cluster from the
Powertrain Control Module (PCM) over the Program-
mable Communications Interface (PCI) data bus. The
check gauges indicator Light Emitting Diode (LED)
receives battery current on the instrument cluster
electronic circuit board through the fused ignition
switch output (run-start) circuit whenever the igni-
tion switch is in the On or Start positions; therefore,
the LED will always be off when the ignition switch
is in any position except On or Start. The LED only
illuminates when it is provided a ground path by the
instrument cluster transistor. The instrument cluster
will turn on the check gauges indicator for the follow-
ing reasons:
• Bulb Test - Each time the ignition switch is
turned to the On position the check gauges indicator
is illuminated for about two seconds as a bulb test.
• Engine Temperature High Message - Each
time the cluster receives a message from the PCM
indicating the engine coolant temperature is about
2001 JEEP WRANGLER
(VFD). The check
receives a message from the PCM indicating a charge
fail condition (system voltage is nine volts or lower),
the check gauges indicator will be illuminated. The
indicator remains illuminated until the cluster
receives a message from the PCM indicating there is
no charge fail condition (system voltage twelve volts
or higher, but lower than sixteen volts) or until the
ignition switch is turned to the Off position, which-
ever occurs first.
receives a message from the PCM indicating a volt-
age high condition (system voltage is sixteen volts or
higher), the check gauges indicator will be illumi-
nated. The indicator remains illuminated until the
cluster receives a message from the PCM indicating
there is no voltage high condition (system voltage is
sixteen volts or lower, but higher than nine volts) or
until the ignition switch is turned to the Off position,
whichever occurs first.
through the actuator test, the check gauges indicator
will be turned on, then off again during the bulb
check portion of the test in order to confirm the func-
tionality of the LED and the cluster control circuitry.
ature, oil pressure, and electrical system voltage,
then sends the proper messages to the instrument
cluster. For further diagnosis of the check gauges
indicator or the instrument cluster circuitry that con-
trols the LED, (Refer to 8 - ELECTRICAL/INSTRU-
MENT CLUSTER - DIAGNOSIS AND TESTING).
For proper diagnosis of the PCM, the PCI data bus,
or the message inputs to the instrument cluster that
control the check gauges indicator, a DRBIII
tool is required. Refer to the appropriate diagnostic
information.
INSTRUMENT CLUSTER
127° C or higher (about 261° F or higher), the check
gauges indicator will be illuminated. The indicator
remains illuminated until the cluster receives a mes-
sage from the PCM indicating that the engine tem-
perature is about 124° C or lower (about 255° F or
lower), or until the ignition switch is turned to the
Off position, whichever occurs first.
• Engine Oil Pressure Low Message - Each
time the cluster receives a message from the PCM
indicating the engine oil pressure is about 0.3 kg/cm
or lower (about 4 psi or lower), the check gauges indi-
cator will be illuminated. The indicator remains illu-
minated until the cluster receives a message from
the PCM indicating that the engine oil pressure is
about 0.6 kg/cm or higher (about 8 psi or higher), or
until the ignition switch is turned to the Off position,
whichever occurs first. The cluster will only turn the
indicator on in response to an engine oil pressure low
message if the engine speed is 300 rpm or greater.
• Charge Fail Message - Each time the cluster
• Voltage High Message - Each time the cluster
• Actuator Test - Each time the cluster is put
The PCM continually monitors the engine temper-
8Js - 19
scan