Supplemental Inflatable Restraint (SIR)

CIRCUIT DESCRIPTION

When the ignition switch is turned to "RUN," the SDM will perform tests to diagnose critical malfunctions within itself. Upon passing these tests
"Ignition 1" 23 VLR and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. The SDM then proceeds to "Continuous Monitoring." The SDM contains a resistor network connected to "Ignition 1," ground, and to Sensor Signal terminal "9." The 1.0 K ohms resistor in the discriminating sensor parallel to the normally open switch provides a parallel path to ground causing a specified percentage of voltage to appear at the Sensor Signal input. This voltage is monitored to detect shorts to ground or a closed discriminating sensor.

DTC WILL SET WHEN

"Ignition 1" is within the normal operating voltage range and the SDM is configured for a discriminating sensor. Once these conditions are met and the discriminating sensor input is below a specified value, DTC 35 will set.

ACTION TAKEN

SDM turns "ON" the "AIR BAG" warning lamp and sets DTC 35.

DTC WILL CLEAR WHEN

The voltage measured at the front end discriminating sensor input is above a specified value for 500 milliseconds.


DTC CHART TEST DESCRIPTION

Numbers below refer to circled numbers on the diagnostic chart.

1. This test checks for a malfunctioning discriminating sensor.

2. This test checks for a short to ground in CKT 1834.


DIAGNOSTIC AIDS

An intermittent condition would likely he caused by a short from CKT 1834 to ground or a malfunctioning discriminating sensor.