R021

Diagnostic Chart:

Wiring Diagram:

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 above 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. This test determines whether the malfunction is in the driver inflator module circuitry or in the SDM wiring harness circuitry.
2. This test checks whether the malfunction is due to a high resistance in CKT 347.
3. This test checks whether the malfunction is due to a high resistance in CKT 348.
4. 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 poor connection at terminals "A" and "B" of the SIR coil connector at the base of the steering column, terminals "A" and "B" of the driver inflator module connector at the top of the steering column, SDM terminals "A1" and "A2" or a poor wire to terminal connection in CKT 347 or CKT 348. The test for this diagnostic trouble code is only run while the "AIR BAG" warning lamp is performing the bulb check, unless DTC RO17 or DTC R026 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.