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 t& Ignition 1," ground, and to Sensor Signal terminal "9." The 1.0 K ohms resistor in the forward discriminating sensor parallel to the normally open switch provides a parallel path to ground causing a specified percentage of "Ignition 1" voltage to appear at the Sensor Signal input. This voltage is monitored to detect shorts to voltage or an open discriminating sensor circuit.

DTC WILL SET WHEN

"Ignition 1" is within its normal operating range and the SDM is configured for a discriminating sensor. Once these conditions are met and the voltage measured at Sensor Signal terminal "9" is above a specified value for 500 milliseconds during "Continuous Monitoring," DTC 36 will set.

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 "9" is in its normal range for 500 milliseconds during "Continuous Monitoring."

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 an open in CKT 1751.

3. This test checks for an open in CKT 1834.

DIAGNOSTIC AIDS

An intermittent condition is likely to be caused an open in CKT 1751 between the discriminating sensor and ground, a poor connection at the discriminating sensor connector or a short in CKT 1834 to B+.