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 "Driver Side Low" and "Passenger Side Low" are NOT below a specified value. Once these conditions are met and the voltage measured at "Driver Side Low" is below a specified value for 500 milliseconds, DTC 24 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 24 and also DTC 71.

DTC WILL CLEAR WHEN
The malfunction is no longer occurring (has been repaired) and the SDM has been replaced. DTC 24 is a latched code and cannot be cleared.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Monitoring "Driv. Senselo" 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 "Driv. Senselo."
2. This test isolates the malfunction to one side of the driver inflator module yellow 2-way connector at the base of the steering column.
3. This test determines if the malfunction is in CKT 347.
4. This test determines if the malfunction is in CKT 348.
5. This test determines if the malfunction is in the SIR coil assembly or the driver inflator module.

DIAGNOSTIC AIDS
An intermittent condition is likely to be caused by a short to ground in the driver inflator module circuit. Inspect CKTs 347 and 348 carefully for cutting or chafing. A careful Inspection of CKTs 347 and 348, Including the SIR coil assembly is essential to ensure that the replacement SDM will not be damaged.