Commander 4WD V8-4.7L VIN N (2006)
Air Bag Deactivation Indicator: Description and Operation
SRS - Airbag Warning Indicator
AIRBAG INDICATOR
DESCRIPTION
An airbag indicator is standard equipment on all instrument clusters. However, the instrument cluster can be programmed to disable this indicator on
vehicles that are not equipped with the airbag system, which is not available in some markets. This indicator is located in the center of the instrument
cluster overlay, between the speedometer and tachometer.
The airbag indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for 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 Light
Emitting Diode (LED) behind the cutout in the opaque layer of the overlay causes the indicator to appear in red through the translucent outer layer of the
overlay when it 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 ineffective 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:
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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.
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ORC Lamp-On Message - Each time the cluster receives a lamp-on message from the ORC, 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 ORC, whichever is longer.
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Communication Error - If the cluster receives no airbag messages for 10 consecutive message cycles, the airbag indicator is illuminated. The
indicator remains illuminated until the cluster receives a single lamp-off message from the ORC.
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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 operating 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, then the instrument cluster and the ORC will each
store a DTC.
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.
