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." "Driver Side Low" terminal "A2" is grounded through a resistor and the driver current source connected to "Driver Side High" terminal "A1" allows a known amount of current to flow. By monitoring the voltage difference between "Driver Side High" and "Driver Side Low" the SDM calculates the combined resistance of the driver inflator module, SIR coil assembly, harness wiring CKTs 347 and 348 and connector terminal contact.

DTC WILL SET WHEN
The combined resistance of the driver inflator module, SIR coil assembly, harness wiring CKTs 347 and 348 and connector terminal contact is below a specified value. This test is run during the "Current Source Diagnostics" when: 1) No "higher priority faults" are detected during "Turn-ON," 2) No "higher priority faults" are detected during "Continuous Monitoring," 3) No "crank" signal present, 4) "Ignition 1" voltage is above a specified value.

ACTION TAKEN
SDM turns "ON" the "AIR BAG" warning lamp and sets a diagnostic trouble code. DTC WILL CLEAR WHEN The ignition switch is turned "OFF."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. DTC 16 and 22 will set simultaneously when the "Driver Side High" circuit is shorted to the "Passenger Side High" circuit due to parallel current paths.
2. This test determines whether the malfunction is in the driver inflator module circuitry or in the SDM wiring harness circuitry.
3. This test checks for a short from the "Driver Side High" circuit to the "Driver Side Low" circuit.
4. This test checks for a short from the "Driver Side High" circuit to the "Passenger Side Low" circuit.
5. This test determines whether the malfunction is in the driver inflator module or the SIR coil assembly.

DIAGNOSTIC AIDS
An intermittent condition is likely to be caused by a short between CKT 347 and CKT 348, CKT 1403 or CKT 1404, or a malfunctioning shorting bar on the driver inflator module or SIR coil assembly which would require replacement of the component. The test for this diagnostic trouble code is only run while "AIR BAG" warning lamp is performing the bulb check, unless DTC 17 or DTC 26 is detected. When a scan tool "Clear Codes" command is issued and the malfunction is still present, the DTC will not reappear until the next ignition cycle.