Operation

OPERATION

The airbag (also known as Supplemental Restraint System/SRS) indicator gives an indication to the vehicle operator when the airbag system, or a circuit or component of the system is ineffective. 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 over the Controller Area Network (CAN) data bus from the Occupant Restraint Controller (ORC) (also known as the lowline or highline airbag control unit/ARCADE).

The airbag indicator Light Emitting Diode (LED) is controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster detects that the ignition switch is in the ON position. Therefore, the LED will always be OFF when the ignition switch is in any position except ON. 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 briefly as a bulb test. The entire bulb test is a function of the ORC.
- Airbag Indicator Lamp-On Message - Each time the cluster receives an electronic airbag indicator lamp-ON message from the ORC, the airbag indicator will be illuminated. The indicator can be flashed ON and OFF, or illuminated solid, as dictated by the ORC message. An indicator illuminated solid indicates an ineffective circuit or component has been detected, while a flashing indicator signals an ORC that is not properly programmed or initialized. The indicator remains illuminated until the cluster receives a lamp-OFF message from the ORC, or until the ignition switch is turned to the OFF position, whichever occurs first. On vehicles equipped with the optional steering wheel buttons, each time the cluster receives an electronic airbag indicator lamp-ON message from the ORC, a SRS, Visit workshop textual message will appear within the cluster multi-function display. The textual message remains displayed until the cluster receives a lamp-OFF message from the ORC, or until the ignition switch is turned to the OFF position, whichever occurs first.

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 ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN or KOMBI). If the ORC sends a lamp-ON message after the bulb test, it indicates that the ORC has detected a system malfunction 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.

For proper diagnosis of the airbag system, the ORC, the EMIC, the CAN data bus or the electronic communication related to airbag indicator operation, a diagnostic scan tool is required. Refer to the appropriate diagnostic information.