For 1990-2009 cars

### Circuit Description

When the ignition switch is turned to ON, the sensing and diagnostic module (SDM) will perform a turn-on test to diagnose critical malfunctions within the SDM itself.

Upon passing these tests, ignition and deployment loop voltages are measured to ensure that they are within their normal voltage ranges. The SDM monitors the voltages at the driver low and the passenger low to detect shorts to ground or voltage in the deployment loops.

The SDM inspects the wiring connection to extra devices such as the side impact sensor by letting the perpetual current flow through the internal circuit and verify the resistance. If the voltage is out of range, the SDM is unable to inspect the air bag system properly.

If the scan tool displays DTC B1103, inspect the battery and replace it with a new one. Erase the DTC using the scan tool.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1103 SIR Serial Communications Fault

### Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

### Conditions for Setting the DTC

The voltage supplied from the battery maintains lower than 10.6 volts for 16 seconds.

### Action Taken When the DTC Sets

The SDM commands the AIR BAG indicator ON.

### Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Warning: Refer to Sensing and Diagnostic Module Voltage after Ignition is Turned Off Warning in the Preface section.

Warning: Refer to Sensing and Diagnostic Module Handling Warning in the Preface section.