Supplemental Inflatable Restraint (SIR)

CIRCUIT DESCRIPTION
When the ignition switch is turned "ON," the SDM will perform tests to diagnose critical malfunctions within itself. Upon passing these tests "Ignition 1," 36 VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. The SDM then proceeds with the "Current Source Diagnostics" followed by "Continuous Monitoring." The SDM supplies "Reference Voltage" at terminal "B6" and measures the voltage at "Sensor Signal" terminal "B5". During normal operation the voltage measured at "Sensor Signal" will be about one half the "Reference Voltage."

DTC WILL SET WHEN
The voltage measured at "Sensor Signal" terminal "B5" is above a specified value for 500 milliseconds during "Continuous Monitoring."

ACTION TAKEN
SDM turns "ON" the "AIR BAG" warning lamp and sets a diagnostic trouble code.

DTC WILL CLEAR WHEN
The voltage measured at "Sensor Signal" terminal "B5" is in its normal range for 500 milliseconds during "Continuous Monitoring."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test checks proper resistance of the forward discriminating sensor.
2. This test checks for a short from the "Reference Voltage" circuit to the "Sensor Signal" circuit.
3. This test checks for a short from "Reference Voltage" to B+.
4. This test checks for a short from "Sensor Signal" to B+.

DIAGNOSTIC AIDS
An intermittent condition is likely to be caused by a short from CKT 349 to CKT 354, a short from CKT 349 to B+, or a short from CKT 354 to B+.