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 B+ in the inflator module circuits.

DTC WILL SET WHEN
"Ignition 1" is within the normal operating voltage range. The voltages of both "Drivers Side Low" and "Passenger Side Low" are NOT above a specified value. Once these conditions are met and the voltage at "Driver Side Low" is above 4.8 volts, DTC 25 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" warning lamp and sets a diagnostic trouble code.

DTC WILL CLEAR WHEN
The voltage measured at "Driver Side Low" is below 4.9 volts for 500 milliseconds.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Recording "Driv. Senselo" before disturbing the system provides a baseline value in case the malfunction turns out to be intermittent.
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 whether the malfunction is in CKT 347.
4. This test determines whether the malfunction is in CKT 348.
5. This test determines whether 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 B+ in the driver inflator module circuit. Monitoring "Driv. Senselo" while moving wires may help locate the circuit malfunction. Inspect CKTs 347, 348, and SIR coil assembly pigtails carefully for cutting or chafing.