Circuit Description
When the ignition is turned ON, the instrument panel cluster (IPC) flashes the AIR BAG indicator seven times. The inflatable restraint sensing and diagnostic module (SDM) performs diagnostic tests on the SIR system and then commands the body control module (BCM) to turn the AIR BAG indicator OFF if no SIR malfunction exists. When the BCM receives the command from the SDM, it sends a serial peripheral interface (SPI) data message to the IPC to turn OFF the AIR BAG indicator. The AIR BAG indicator is indirectly controlled by the SDM via Class 2 serial data and SPI data. If the Ignition 1 voltage to the SDM is outside of the normal operating voltage range of 9-16 volts, the SDM will command the BCM to command the IPC, through SPI data, to turn the AIR BAG indicator ON with no diagnostic trouble codes (DTCs) present.
Diagnostic Aids
If Class 2 serial data communications is lost between the SDM and the BCM, the BCM will command the IPC to turn the AIR BAG indicator ON. For more detailed information concerning the Class 2 serial data lines, refer to Data Link Communications Description and Operation in Data Link Communications. If SPI data is lost between the BCM and the IPC, the IPC will turn the AIR BAG indicator ON. For more detailed information concerning the SPI data lines, refer to Body Control System Description and Operation in Body Control System.
The following are possible causes of the malfunction:
| • | Ignition 1 voltage out of range |
| • | An internal IPC malfunction |
| • | An internal BCM malfunction |
| • | An internal SDM malfunction |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests to see if the Ignition 1 voltage is more than 9 V.
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This step tests to see if the Ignition 1 voltage is more than 16 V.
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This step tests to see if the SDM connector is damaged or corroded.
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This step tests for an open or high resistance in the Ignition 1 voltage feed circuit to the SDM.
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This step tests for an open or high resistance in the Ignition 1 voltage feed circuit to the AIR BAG Fuse.
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This step tests for an open or high resistance in the SDM ground circuit.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: SIR Schematics | ||||
1 | Did you perform the Diagnostic System Check-SIR? | -- | Go to Step 2 | |
2 |
Does the AIR BAG indicator flash seven times? | -- | Go to Step 4 | Go to Step 3 |
3 | Replace the IPC. Refer to Instrument Cluster Replacement in Instrument Panel, Gages and Console. Did you complete the replacement? | -- | Go to Step 12 | -- |
4 | Note the AIR BAG indicator after it has flashed seven times. Does the AIR BAG indicator turn OFF after flashing seven times? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 5 |
With a scan tool, observe the SIR data list display. Does the scan tool indicate that the ignition voltage is greater than the specified value? | 9 V | Go to Step 6 | Go to Step 7 | |
Does the scan tool indicate that the ignition voltage is greater than the specified value? | 16 V | Go to Diagnostic System Check - Engine Electrical in Engine Electrical | Go to Step 11 | |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 | |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | |
Test the Ignition 1 voltage feed circuit to the AIR BAG Fuse for an open or high resistance. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | |
11 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2 |
