Dodge Dakota 2001, Service Manual

Page: 442 / 2307

The CTM provides a hard wired ground input to
the instrument cluster circuitry through the VTSS
indicator driver circuit whenever the ignition switch
is in the Off position and the VTSS is arming, armed,
or triggered. Whenever the ignition switch is in the
On or Start positions, the SKIM performs a self-test
to decide whether the system is in good operating
condition. The SKIM then sends the proper lamp-on
or lamp-off messages to the instrument cluster. For
further diagnosis of the security indicator or the
instrument cluster circuitry that controls the indica-
tor,
(Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). If the
SKIS turns on the security indicator after the bulb
test, either solid or flashing, it indicates that a SKIS
malfunction has occurred or that the SKIS is inoper-
ative. The VTSS indicator driver circuit input to the
instrument cluster can be diagnosed using conven-
tional diagnostic tools and methods. For proper diag-
nosis of the VTSS, the CTM, the SKIS, the PCI data
bus, or the message inputs to the instrument cluster
that control the security indicator, a DRBIII
t
scan
tool is required. Refer to the appropriate diagnostic
information.
SERVICE 4WD INDICATOR
DESCRIPTION
A service 4WD indicator is standard equipment on
all instrument clusters. However, on vehicles not
equipped with the optional four-wheel drive system
and electronically shifted transfer case, this indicator
is electronically disabled. The service 4WD indicator
is located in the Information Center area of the
instrument cluster, to the right of center. The service
4WD indicator consists of a stencilled cutout of the
words “SERVICE 4WD” 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. An amber lens
behind the cutout in the opaque layer of the overlay
causes the “SERVICE 4WD” text to appear in amber
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 service
4WD indicator is serviced as a unit with the instru-
ment cluster.
OPERATION
The service 4WD indicator gives an indication to
the vehicle operator when the Transfer Case Control
Module (TCCM) has recorded a Diagnostic Trouble
Code (DTC) for an electronic transfer case circuit or
component malfunction. This indicator is controlled
by a transistor on the instrument cluster circuit
board based upon cluster programming and elec-
tronic messages received by the cluster from the
TCCM
over the Programmable Communications
Interface (PCI) data bus. The service 4WD 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
service 4WD indicator for the following reasons:
•
Bulb Test - Each time the ignition switch is
turned to the On position the service 4WD indicator
is illuminated for about two seconds as a bulb test.
•
Service 4WD Lamp-On Message - Each time
the cluster receives a lamp-on message from the
TCCM, the indicator will be illuminated. The indica-
tor remains illuminated until the cluster receives a
service 4WD lamp-off message from the TCCM, or
until the ignition switch is turned to the Off position,
whichever occurs first.
•
Communication Error - If the cluster receives
no messages from the TCCM for six seconds, the ser-
vice 4WD indicator is illuminated by the instrument
cluster to indicate a loss of TCCM communication.
The indicator remains controlled and illuminated by
the cluster until a valid message is received from the
TCCM.
•
Actuator Test - Each time the cluster is put
through the actuator test, the service 4WD indicator
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 TCCM continually monitors the electronic
transfer case switch and circuits to determine the
condition of the system, then sends the proper mes-
sages to the instrument cluster. For further diagnosis
of the service 4WD indicator or the instrument clus-
ter circuitry that controls the LED, (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER - DIAGNO-
SIS AND TESTING). For proper diagnosis of the
TCCM, the PCI data bus, or the message inputs to
the instrument cluster that control the service 4WD
indicator, a DRBIII
t
scan tool is required. Refer to
the appropriate diagnostic information.
SPEEDOMETER
DESCRIPTION
A speedometer is standard equipment on all instru-
ment clusters. The speedometer is located next to the
AN
INSTRUMENT CLUSTER 8J - 29
SECURITY INDICATOR (Continued)