Supplemental Inflatable Restraint (SIR)

Diagnostic Chart:

Wiring Diagram:

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 monitors the voltages at "Driver Side Low" terminal "3" and "Passenger Side Low" terminal "4" to detect shorts to ground in the inflator module circuits. The service wait time is 10 minutes. Refer to enable/disable procedures before replacing SIR components.

DTC WILL SET WHEN
Neither of the two inflator module circuits is open. "Ignition 1" is within the normal operating voltage range. The voltages of both "Drivers Side Low" and "Passenger Side Low" are NOT below a specified value. Once these conditions are met and the voltage at "Passenger Side Low" is below a specified value, DTC 18 will set. This test is run during "Turn-ON" tests and every 100 milliseconds during "Continuous Monitoring.

ACTION TAKEN
SDM turns "ON" the "AIR BAG" indicator, sets DTC 18 and also DTC 71.

DTC WILL CLEAR WHEN
The malfunction is no longer occurring (has been repaired) and the SDM has been replaced. DTC 18 is a latched code and cannot he cleared.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Monitoring "Pass. Sense lo" may help to locate the fault. The value displayed by the TECH 1 is updated continuously so that intermittent shorts can be located by moving wires while monitoring "Pass. Senselo."
2. This test checks for a malfunctioning passenger inflator module.
3. This test determines if the malfunction is in CKT 1403.
4. This test determines if the malfunction is in CKT 1404.
5. This test determines if the malfunction is in the passenger inflator module jumper.

DIAGNOSTIC AIDS
An intermittent condition is likely to be caused by a short to ground in the passenger inflator module circuit. A DTC 18 would be accompanied by DTC 71. Inspect CKTs 1403 and 1404 carefully for cutting or chafing. If the wiring pigtail of the passenger inflator module is damaged the component must he replaced. A careful Inspection of the circuits and components Indicated on the DTC 18 chart Is essential to ensure that the replacement SDM will not be damaged.