AIRBAG INDICATOR
DESCRIPTION
An airbag indicator is standard equipment on all
instrument
clusters.
However,
on
vehicles
not
equipped with airbags, this indicator is electronically
disabled. The airbag indicator is located in the Infor-
mation Center area of the instrument cluster, to the
right of center. The airbag indicator consists of a
stenciled cutout of the word “AIRBAG” 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 “AIRBAG” text to appear in red
through the translucent outer layer of the overlay
when it is illuminated from behind by a Light Emit-
ting Diode (LED) soldered onto the instrument clus-
ter electronic circuit board. The airbag indicator is
serviced as a unit with the instrument cluster.
OPERATION
The airbag indicator gives an indication to the
vehicle operator when the airbag system is faulty or
inoperative. The airbag indicator is controlled by a
transistor on the instrument cluster circuit board
based upon cluster programming and electronic mes-
sages received by the cluster from the Airbag Control
Module (ACM) over the Programmable Communica-
tions Interface (PCI) data bus. The airbag 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 indicator 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 airbag indicator for the following reasons:
• Bulb Test - Each time the ignition switch is
turned to the On position the airbag indicator is illu-
minated for about seven seconds. The first two sec-
onds is the cluster bulb test function, and the
remainder is the ACM bulb test function.
• ACM Lamp-On Message - Each time the clus-
ter receives a lamp-on message from the ACM, the
airbag indicator will be illuminated. The indicator
remains illuminated for about twelve seconds or until
the cluster receives a lamp-off message from the
ACM, whichever is longer.
• Communication Error - If the cluster receives
no airbag messages for three consecutive seconds, the
airbag
indicator
is
illuminated.
The
indicator
remains illuminated for about twelve seconds or until
the cluster receives a single lamp-off message from
the ACM, whichever is longer.
• Actuator Test - Each time the cluster is put
through the actuator test, the airbag 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 ACM continually monitors the airbag system
circuits and sensors to decide whether the system is
in good operating condition. The ACM then sends the
proper lamp-on or lamp-off messages to the instru-
ment cluster. If the ACM sends a lamp-on message
after the bulb test, it indicates that the ACM has
detected a system malfunction and/or that the air-
bags may not deploy when required, or may deploy
when not required. The ACM will store a Diagnostic
Trouble Code (DTC) for any malfunction it detects.
Each time the airbag indicator fails to illuminate due
to an open or short in the cluster airbag indicator cir-
cuit, the cluster sends a message notifying the ACM
of the condition. The ACM will store a DTC and the
cluster will begin blinking the seat belt indicator.
(Refer to 8 - ELECTRICAL/INSTRUMENT CLUS-
TER/SEATBELT INDICATOR - OPERATION). For
proper diagnosis of the airbag system, the ACM, the
PCI data bus, or the message inputs to the instru-
ment cluster that control the airbag indicator, a
DRBIII
t scan tool is required. Refer to the appropri-
ate diagnostic information.
BRAKE/PARK BRAKE
INDICATOR
DESCRIPTION
A brake indicator is standard equipment on all
instrument clusters. The brake indicator is located in
the Information Center area of the instrument clus-
ter, to the right of center. The brake indicator con-
sists of a stenciled cutout of the word “BRAKE” and
the International Control and Display Symbol icons
for “Brake Failure” and “Parking 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 lens behind the cutout in the opaque layer of
the overlay causes the “BRAKE” text and the two
icons 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) sol-
dered onto the instrument cluster electronic circuit
board. The brake indicator is serviced as a unit with
the instrument cluster.
8J - 14
INSTRUMENT CLUSTER
AN