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 driver inflator module, the SIR coil assembly, 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 a specified value for 500 milliseconds during "Deployment Loop Continuity" or "Continuous Monitoring.


ACTION TAKEN:

SDM turns "ON" the "AIR BAG" indicator 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 a specified value 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 yellow 2-way connector at the base of the steering column.

2. This test checks for proper contact and/or corrosion of the yellow 2-way connector at the base of the steering column.

3, This test isolates the malfunction to one side of the driver inflator module yellow 2-way connector located at the base of the steering column.

4. This test determines if the malfunction is due to an open in the wiring.

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 poor connection 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. An intermittent open in the SIR coil assembly could also set this DTC. To test for a bad SIR coil assembly, clear DTCs, then turn the steering wheel back and forth with the ignition switch in "RUN." If the "AIR BAG" indicator comes "ON" and DTC 26 has set again, it is likely the SIR coil assembly is malfunctioning.