Dodge Dakota 2001, Service Manual

Page: 428 / 2307

OPERATION
The brake indicator gives an indication to the vehi-
cle operator when the parking brake is applied, or
when there are certain brake hydraulic system mal-
functions. 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 Central Timer Mod-
ule (CTM) and the Controller Antilock Brake (CAB)
over the Programmable Communications Interface
(PCI) data bus. The brake indicator Light Emitting
Diode (LED) receives battery current on the instru-
ment cluster electronic circuit board through the
fused ignition switch output (run-start) circuit when-
ever the ignition switch is in the On or Start posi-
tions; 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 path
to ground by the instrument cluster transistor. The
instrument cluster will turn on the brake indicator
for the following reasons:
•
Bulb Test - Each time the ignition switch is
turned to the On position the brake indicator is illu-
minated by the instrument cluster for about four sec-
onds as a bulb test.
•
Brake Lamp-On Message - Each time the
cluster receives a lamp-on message from the CTM or
the CAB, the brake indicator will be illuminated. If
the park brake is applied or not fully released, or if
the pressures in the two halves of the split brake
hydraulic system are not equal with the ignition
switch in the On position, the brake indicator is illu-
minated solid. The brake indicator will blink on and
off repeatedly when the park brake is applied or not
fully released and the ignition switch is in the On
position if a vehicle with an automatic transmission
is not in Park or Neutral, or if the engine is running
on vehicles with a manual transmission. The indica-
tor remains illuminated until the cluster receives
lamp-off messages from both the CTM and the CAB,
or until the ignition switch is turned to the Off posi-
tion, whichever occurs first.
•
Actuator Test - Each time the instrument clus-
ter is put through the actuator test, the brake indi-
cator will be turned on, then off again during the
bulb check portion of the test to confirm the function-
ality of the LED and the cluster control circuitry.
The park brake switch on the park brake pedal
mechanism provides a hard wired ground input to
the CTM circuitry through the park brake switch
sense circuit whenever the park brake is applied or
not fully released. The CTM then sends the proper
lamp-on or lamp-off messages to the instrument clus-
ter. The brake pressure switch on the brake combina-
tion valve provides a hard wired ground input to the
CAB circuitry through the brake pressure switch
sense circuit whenever the pressures in the two
halves of the split brake hydraulic system are
unequal. The CAB then sends the proper lamp-on or
lamp-off messages to the instrument cluster. If the
CAB sends a lamp-on message after the bulb test, it
indicates that the CAB has detected a brake hydrau-
lic system malfunction and/or that the ABS system
has become inoperative. The CAB will store a Diag-
nostic Trouble Code (DTC) for any malfunction it
detects. The park brake switch input to the CTM and
the brake pressure switch input to the CAB can be
diagnosed using conventional diagnostic tools and
methods. For proper diagnosis of the antilock brake
system, the CTM, the CAB, the PCI data bus, or the
message inputs to the instrument cluster that control
the brake indicator, a DRBIII
t
scan tool is required.
Refer to the appropriate diagnostic information.
CHECK GAUGES INDICATOR
DESCRIPTION
A check gauges indicator is standard equipment on
all instrument clusters. The check gauges indicator is
located in the Information Center area of the instru-
ment cluster, to the right of center. The check gauges
indicator consists of a stenciled cutout of the words
“CHECK GAGES” in the opaque layer of the instru-
ment cluster overlay. The dark outer layer of the
overlay prevents the indicator from being clearly vis-
ible when it is not illuminated. A red lens behind the
cutout in the opaque layer of the overlay causes the
“CHECK GAGES” 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 check gauges indicator is
serviced as a unit with the instrument 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 circuit board based
upon cluster programming and electronic messages
received by the cluster from the Powertrain Control
Module (PCM) over the Programmable Communica-
tions Interface (PCI) data bus. The check gauges
indicator Light Emitting Diode (LED) receives bat-
tery current on the instrument cluster electronic cir-
cuit 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 posi-
tion except On or Start. The LED only illuminates
AN
INSTRUMENT CLUSTER 8J - 15
BRAKE/PARK BRAKE INDICATOR (Continued)