Supplemental Inflatable Restraint (SIR)

When measurements are requested in this chart, use SA 91114NE DVM with correct terminal adapter from SA 9206Z. When a check for proper connection is requested, refer to "Intermittents and Poor Connections." When a wire connector or terminal repair is requested, use the proper repair parts and refer to "Wiring Repair."

CAUTION: BEFORE PERFORMING DIAGNOSTICS, THE IGNITION SWITCH MUST BE IN THE "OFF" POSITION FOR 10 MINUTES (REFER TO DISABLING AND ENABLING PRECAUTIONS).

NOTICE: Perform "SIR DIAGNOSTIC SYSTEM CHECK" before proceeding with this chart. SIR Diagnostic System Check

CIRCUIT DESCRIPTION
When the ignition switch is turned On, the Sensing and Diagnostic Module (SDM) will perform tests to diagnose critical malfunctions within itself. Upon passing these tests "Ignition 1," 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 LO" terminal A3 is grounded through a resistor and the driver current source connected to "Driver Side HI" terminal A2 allows a known amount of current to flow. After "Current Source Diagnostics" are completed the SDM removes the low resistance ground from "Driver Side LO" and switches the driver current source at "Driver Side HI." The SDM then measures the voltage at "Driver Side HI" and "Driver Side LO"during "Continuous Monitoring." By monitoring the voltage difference between "Driver Side HI" and "Driver Side LO" the SDM calculates the combined resistance of the SIR coil assembly, driver inflator module, harness wiring circuits 347 and 348 and connector terminal contact.

DTC WILL SET WHEN:
The combined resistance of the SIR coil assembly, driver inflator module, harness wiring circuits 347 and 348 and connector terminal contact is greater than 500 ohms for 500 milliseconds during "Current Source Diagnostic" or "Continuous Monitoring."

ACTION TAKEN:
SDM turns On the AIR BAG telltale lamp and sets DTC 26. DTC 26 will take precedence over DTCs 15, 16, 18, 21, 22 and 24.

DTC WILL CLEAR WHEN:
The voltage difference between "Driver Side HI" terminal A2 and "Driver Side LO" terminal A3 is less than 100 ohms for 500 milliseconds during "Continuous Monitoring."

DTC CHART TEST DESCRIPTION:
Number(s) below refer to step number(s) on the diagnostic chart.
Step 1. This test determines whether the malfunction is in the driver inflator module circuitry or in the SDM wiring harness circuitry.
Step 2. This test determines whether the malfunction is due to a high resistance in circuit 347.
Step 3. This test determines whether the malfunction is in the driver inflator module or the SIR coil assembly.
Step 4. This test determines whether the malfunction is due to a high resistance in circuit 348.

DIAGNOSTIC AIDS:
An intermittent condition is likely to be caused by a poor connection at the driver inflator module terminals A and B, SIR coil assembly terminals A and B, SDM terminals A2 and A3 or an open in circuit 347 or 348.