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 icon 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 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 messages received by the cluster from the Occupant Restraint Controller (ORC) over the Controller
Area Network (CAN) data bus.
The airbag 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 current 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 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 illuminated for
about six to eight seconds. The entire bulb test is a function of the ORC.
•
ORC Lamp-On Message - Each time the cluster receives a lamp-on message from the ORC, the airbag indi-
cator will be illuminated. The indicator remains illuminated for about twelve seconds or until the cluster
receives a lamp-off message from the ORC, whichever is longer.
•
Communication Error - If the cluster receives no airbag messages for ten consecutive message cycles, the
airbag indicator is illuminated. The indicator remains illuminated until the cluster receives a single lamp-off
message from the ORC.
•
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 portion of the test to confirm the functionality of the LED and the cluster
control circuitry. The actuator test illumination of the airbag indicator is a function of the instrument cluster.
The ORC continually monitors the airbag system circuits and sensors to decide whether the system is in good oper-
ating condition. The ORC then sends the proper lamp-on or lamp-off messages to the instrument cluster. If the ORC
sends a lamp-on message after the bulb test, it indicates that the ORC has detected a system malfunction and/or
that the airbags and seat belt tensioners may not deploy when required, or may deploy when not required. The
ORC 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 circuit, the cluster sends a message notifying the
ORC of the condition, the instrument cluster and the ORC will each store a DTC, and the cluster will flash the
seatbelt indicator on and off as a backup to notify the vehicle operator.
For proper diagnosis of the airbag system, the ORC, the CAN data bus, or the electronic message inputs to the
instrument cluster that control the airbag indicator, a diagnostic scan tool is required. Refer to the appropriate diag-
nostic information.
BRAKE/PARK BRAKE INDICATOR
DESCRIPTION
A brake indicator is standard equipment on all instru-
ment clusters. This indicator is located in the center of
the speedometer, in the area below and right of the
speedometer needle hub.
The brake indicator consists of a stencil-like cutout of the word “BRAKE” (all clusters with a miles-per-hour primary
speedometer scale), or the International Control and Display Symbol icon for “Brake Failure” (all clusters with a
kilometers-per-hour primary scale) 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 or the icon to appear in red through
the translucent outer layer of the overlay when the indicator is illuminated from behind by the LED, which is sol-
dered onto the instrument cluster electronic circuit board. The brake indicator is serviced as a unit with the instru-
ment cluster.
HB
CLUSTER
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