Circuit Description

When ignition is turned on, Sensing and Diagnostic Module (SDM) performs tests to diagnose critical internal malfunctions. Ignition voltage and deployment loop voltages are measured to ensure they are within normal ranges. SDM proceeds with resistance measurement test. Driver-side low terminal No. 4 (Yellow/Black wire) is grounded through current sink and driver current source connected to driver-side high terminal No. 3 (Yellow wire) allows a known amount of current to flow. By monitoring voltage difference between driver-side high and low circuits, SDM calculates combined resistance of driver-side air bag, SRS coil assembly, harness wiring circuits IB05 (Yellow wire) and IB06 (Yellow/Black wire) and connector terminal contacts.