AIR BAG Indicator Circuit Malfunction

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 IPC to turn the AIR BAG indicator OFF if no SIR malfunction exists. The AIR BAG indicator is controlled by the SDM via Class 2 serial data. If the ignition 1 voltage is outside of the normal operating voltage range 9-16 volts, the SDM will command the IPC to turn the AIR BAG indicator ON with no diagnostic trouble codes (DTCs) present.

DIAGNOSTIC AIDS
The IPC will turn the AIR BAG indicator ON if there is a loss of serial data communication between the IPC and the SDM. For more detailed information concerning the Class 2 data lines, refer to Data Link Communications Description and Operation in Data Link Communications.

The following are possible causes of the malfunction:
- Ignition 1 voltage out of range
- An internal IPC malfunction
- An internal SDM malfunction

TEST DESCRIPTION

Steps 1-4:

Steps 5-8:

Steps 9-13:

The numbers below refer to the step numbers on the diagnostic table.
5. Tests to see if the scan tool can communicate with the IPC.
6. Tests to see if the ignition 1 voltage is more than 9 V.
7. Tests to see if the ignition 1 voltage is more than 16 V.
8. Tests to see if the SDM connector is damaged or corroded.
9. Tests to see if there is an open or high resistance in the ignition 1 voltage feed circuit to the SDM.
10. Tests to see if there is an open or a high resistance in the ignition 1 voltage feed circuit to the SIR Fuse.
11. Tests to see if there is an open or a high resistance in the SDM ground circuit.