Circuit Description

When ignition is turned on, Sensing and Diagnostic Module (SDM) performs tests to diagnose critical internal malfunctions. Upon passing these tests, ignition and deployment loop voltages are measured to ensure they are within normal ranges. During continuous monitoring diagnostics, a fixed amount of current is flowing in deployment loop. This produces proportional voltage drops in loop. By monitoring voltage difference between driver-side high and low circuits, SDM calculates combined resistance of driver-side air bag, SRS coil, harness wiring circuits IB05 (Yellow wire) and IB06 (Yellow/Black wire) and connector terminal contacts.