Dodge Dakota 2001, Service Manual

Page: 429 / 2307

when it is provided a path to ground by the instru-
ment cluster transistor. The instrument cluster will
turn on the check gauges indicator for the following
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 of a gaso-
line engine is about 122° C (253° F) or higher, or a
diesel engine is about 112° C (233° F) or higher, the
check gauges indicator will be illuminated. The indi-
cator remains illuminated until the cluster receives a
message from the PCM indicating that the tempera-
ture of a gasoline engine is about 119° C (246° F) or
lower, a diesel engine is about 109° C (226° 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 of a gasoline
engine is about 3.45 kPa (0.5 psi) or lower, or a diesel
engine is about 51.71 kPa (7.5 psi) or lower, the
check gauges indicator will be illuminated. The indi-
cator remains illuminated until the cluster receives a
message from the PCM indicating that the engine oil
pressure of a gasoline engine is above 3.45 kPa (0.5
psi), a diesel engine is above 51.71 kPa (7.5 psi), 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 greater than zero.
•
System Voltage Low Message - Each time the
cluster receives a message from the PCM indicating
the electrical system voltage is less than 11.5 volts,
the check gauges indicator will be illuminated. The
indicator
remains illuminated until the cluster
receives a message from the PCM indicating the elec-
trical system voltage is greater than 12.0 volts (but
less than 16.6 volts), or until the ignition switch is
turned to the Off position, whichever occurs first.
•
System Voltage High Message - Each time
the cluster receives a message from the PCM indicat-
ing the electrical system voltage is greater than 16.6
volts, the check gauges indicator will be illuminated.
The indicator remains illuminated until the cluster
receives a message from the PCM indicating the elec-
trical system voltage is less than 16.1 volts (but
greater than 11.5 volts), or until the ignition switch
is turned to the Off position, whichever occurs first.
•
Actuator Test - Each time the cluster is put
through the actuator test, the indicator will be
turned on, then off again during the bulb check por-
tion of the test to confirm the functionality of the
LED and the cluster control circuitry.
The PCM continually monitors the engine temper-
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
t
scan
tool is required. Refer to the appropriate diagnostic
information.
COOLANT LOW INDICATOR
DESCRIPTION
A coolant low indicator is only found in the instru-
ment clusters of vehicles equipped with an optional
diesel engine. The coolant low indicator is located in
the Information Center area of the instrument clus-
ter, to the left of center. The coolant low indicator
consists of a stenciled cutout of the words “LOW
COOLANT” 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 cut-
out in the opaque layer of the overlay causes the
“LOW COOLANT” text to appear in red through the
translucent outer layer of the overlay when the indi-
cator is illuminated from behind by a Light Emitting
Diode (LED) soldered onto the instrument cluster
electronic circuit board. The coolant low indicator is
serviced as a unit with the instrument cluster.
OPERATION
The coolant low indicator gives an indication to the
vehicle operator when the engine coolant level is low.
This indicator is controlled by a transistor on the
instrument cluster circuit board based upon cluster
programming and electronic messages received by
the cluster from the Powertrain Control Module
(PCM)
over the Programmable Communications
Interface (PCI) data bus. The coolant low 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 ignition 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 pro-
vided a path to ground by the instrument cluster
transistor. The instrument cluster will turn on the
coolant low indicator for the following reasons:
8J - 16 INSTRUMENT CLUSTER
AN
CHECK GAUGES INDICATOR (Continued)