Brake/Park Brake Indicator Description; Operation; Diagnosis And Testing - Brake Indicator - Chrysler Vehicle User Manual

8J - 22 INSTRUMENT CLUSTER
BRAKE/PARK BRAKE
INDICATOR
DESCRIPTION
A brake indicator is standard equipment on all
instrument clusters. The brake indicator is located
near the lower edge of the instrument cluster, to the
left of center. The brake indicator consists of a sten-
cil-like cutout of the word "BRAKE" 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
Light Emitting Diode (LED) behind the cutout in the
opaque layer of the overlay causes the "BRAKE" text
to appear in red through the translucent outer layer
of the overlay when the indicator is illuminated from
behind by the LED, which is soldered onto the
instrument cluster electronic circuit board. The brake
indicator is serviced as a unit with the instrument
cluster.

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, electronic messages received by
the cluster from the Powertrain Control Module
(PCM) over the Programmable Communications
Interface (PCI) data bus, and hard wired inputs to
the instrument cluster from the park brake switch
and the brake warning indicator switch. The brake
indicator Light Emitting Diode (LED) is completely
controlled by the instrument cluster logic circuit, and
that logic will only allow this indicator to operate
when the instrument cluster receives a battery cur-
rent input on the fused ignition switch output (run-
start) circuit. Therefore, the LED will always be off
when the ignition switch is in any position except On
or Start. The cluster can illuminate the LED solid, or
flash it on and off at about one flash per second. 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.
• Park Brake Switch Input - Each time the
cluster detects ground on the red brake warning indi-
cator driver circuit (park brake switch closed = park
brake applied or not fully released) the brake indica-
tor is illuminated solid. If a vehicle speed message is
received by the cluster from the PCM over the PCI
data bus indicating the vehicle is moving while the
red brake warning
grounded, the brake indicator is flashed on and off
repeatedly. Whether illuminated solid or flashing, the
indicator remains illuminated until the red brake
warning indicator driver input to the cluster is an
open circuit (park brake switch open = park brake
fully released), or until the ignition switch is turned
to the Off position, whichever occurs first.
• Brake Hydraulic System Malfunction - Each
time the cluster detects ground on the red brake
warning indicator driver circuit (brake warning indi-
cator switch closed = pressures in the two halves of
the split brake hydraulic system are unequal) the
brake indicator is illuminated solid. The indicator
remains illuminated until the red brake warning
indicator driver input to the cluster is an open circuit
(brake warning indicator switch open = brake
hydraulic system pressures are equal), or until the
ignition switch is turned to the Off position, which-
ever 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 and the brake warning
pressure switch are each connected in parallel
between ground and the red brake warning indicator
driver input to the instrument cluster so that each of
their inputs will illuminate the indicator indepen-
dently of the other. The park brake switch and brake
warning indicator switch inputs to the instrument
cluster can be diagnosed using conventional diagnos-
tic tools and methods. (Refer to 5 - BRAKES/PARK-
ING BRAKE - OPERATION). (Refer to 5 - BRAKES/
ELECTRICAL/BRAKE
OPERATION).
For further diagnosis of the brake indicator or the
instrument cluster circuitry that controls the LED,
(Refer to 8 - ELECTRICAL/INSTRUMENT CLUS-
TER - DIAGNOSIS AND TESTING). For proper
diagnosis of the PCM, the PCI data bus, or the mes-
sage inputs to the instrument cluster that control the
brake indicator, a DRBIII
Refer to the appropriate diagnostic information.

DIAGNOSIS AND TESTING - BRAKE INDICATOR

The diagnosis found here addresses an inoperative
brake indicator condition. If there are problems with
several indicators in the instrument cluster, (Refer to
8 - ELECTRICAL/INSTRUMENT CLUSTER - DIAG-
NOSIS AND TESTING). If the brake indicator stays
on with the ignition switch in the On position and
the park brake released, or comes on while driving,
indicator driver input
PRESSURE SWITCH
scan tool is required.
TJ
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