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. During "Deployment Loop Continuity" and "Continuous Monitoring" diagnostics, a fixed amount of current is flowing in the deployment loop. This produces proportional voltage drops in the loop. By monitoring the voltage difference between "Driver Side High" and "Driver Side Low" the SDM calculates the combined resistance of the passenger inflator module, harness wiring CKTs 347 and 348 and connector terminal contact.

DTC WILL SET WHEN
The voltage difference between "Driver Side High" terminal "2" and "Driver Side Low" terminal "3" is above or equal to 0.400 volts for 500 milliseconds during "Deployment Loop Continuity" or "Continuous Monitoring."

ACTION TAKEN
SDM turns "ON" the "AIR BAG" warning lamp and sets a diagnostic trouble code.

DTC WILL CLEAR WHEN
The voltage difference between "Driver Side High" terminal "2" and "Driver Side Low" terminal "3" is below 0.400 volts for 500 milliseconds during "Continuous Monitoring."

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test verifies proper connection of the driver inflator module yellow 2-way connector and checks for a high resistance, or open, within the connector.
2. This test isolates the high resistance, or open, to either the driver inflator module/SIR coil assembly or CKTs 347 and 348.
3. A high resistance has been detected in CKTs 347 and/or 348. This test checks CKT 347 for high resistance or an open.
4. This test checks CKT 348 for high resistance or an open.
5. If the malfunction cannot be found in the external wiring, the SDM may be malfunctioning.
6. If the SIR coil assembly pigtail connector terminals are damaged or corroded, the SIR coil assembly must be replaced.
7. 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 poor connection inside the SIR coil assembly, at the driver inflator module terminals "A" or "B," SIR coil assembly terminals "A" or "B," SDM terminals "2" or "3," or an open in CKT 347 or CKT 348. To test for a bad SIR coil assembly, clear any DTCs, then turn the steering wheel back and forth with the ignition switch in "RUN." If the "AIR BAG" warning lamp comes "ON" and DTC 26 has reset, it is likely the SIR coil assembly is malfunctioning. Monitoring DTC 26 (to see if current or history) while moving wires may help locate the circuit malfunction.