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 monitors the voltage at "Driver Side LO" terminal A3 and "Passenger Side LO" terminal A4 to detect shorts to B+ or ignition in the inflator module circuits.

DTC WILL SET WHEN:
The VLR power supply in the SDM is in its normal operating voltage range and neither of the two inflator modules is open. Then, if the voltage measured at "Driver Side LO" is greater or equal to five volts, and the voltage measured at "Passenger Side LO" is less than five volts for 500 milliseconds during "Continuous Monitoring" or "Current Source Diagnostics," DTC 25 will set.

ACTION TAKEN:
SDM turns On the AIR BAG telltale lamp, sets DTC 25. DTC 25 will take precedence over DTCs 15, 16, 28, 21 and 22.

DTC WILL CLEAR WHEN:
The voltage measured at "Driver Side LO" is less than four volts for 500 milliseconds during "Continuous Monitoring." Or, the malfunction no longer exists and the ignition is turned Off.

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 occurring in the driver inflator module, coil assembly, or the circuitry.
Step 4. This test checks for a short from "Driver Side HI" to B+ or ignition.
Step 6. This test checks for a short from "Driver Side LO" to B+ or ignition, or an SDM integrity problem.

DIAGNOSTIC AIDS:
An intermittent condition is likely to be caused by a short to B+ or ignition in the driver inflator module circuits. Inspect circuits 347 and 348 carefully for cutting or chafing. If the wiring pigtail of the SIR coil assembly or the driver inflator module is damaged, the component must be replaced.