Air Bag Indicator Always On

AIR BAG INDICATOR ALWAYS ON

CIRCUIT DESCRIPTION
The ignition switch supplies battery voltage to the AIR BAG indicator using the instrument panel fuse. The AIR BAG indicator is controlled by the sensing and diagnostic module (SDM) via universal asynchronous receiver transmitter (UART) data. When the ignition switch is first turned to the ON position, the SDM responds by illuminating the AIR BAG indicator for approximately 6 seconds while performing diagnostic tests on the SIR system.

DIAGNOSTIC AIDS
Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:
- An open or high resistance in serial data line
- A misconstrued instrument cluster
- Battery voltage below 8 volts or above 21.2 volts
- Seat belt pretensioners have deployed
- SDM has deployed
- SDM does not receive a poll from the body control module (BCM)
- An open or high resistance in the SDM ground circuit
- A open, high resistance or short to ground in the SDM ignition voltage circuit
- An internal SDM malfunction
- An internal BCM malfunction

If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections.

TEST DESCRIPTION

Step 1 - Step 12:

Step 13 - Step 21:

The numbers below refer to the step numbers on the diagnostic table.
3. This step tests for serial data communication between the SDM and the scan tool.
5. This step tests for proper instrument panel cluster (IPC) configuration.
6. This step tests for communication with other modules.
7. This step tests for a deployed SDM.
8. This step tests the SDM ignition voltage circuit.
9. This step tests the SDM ignition voltage (after 3 seconds).
11. This step tests for a battery malfunction.
12. This step tests for a charging system malfunction.
13. This step tests the SDM ignition voltage circuit.
15. This step tests the SDM ground circuit.
16. This step tests the SDM serial data line to the IPC.