Supplemental Inflatable Restraint (SIR)

Diagnostic Chart:

Diagnostic Chart (Cont'd):

Circuit Schematic:

CIRCUIT DESCRIPTION
When the ignition switch is turned On, the Sensing & Diagnostics Module (SDM) will perform tests to diagnose critical malfunctions within itself. Upon passing these tests "Ignition 1," 36 VLR (Voltage Loop Energy Reserve), and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. The SDM monitors the voltage at "Driver Side Low" and terminal A2 and "Passenger Side Low" terminal A6 to detect shorts to B+ or ignition in the inflator module circuits.

DTC WILL SET WHEN:
The 36 VLR power supply in the SDM is in its normal operating voltage range and neither of the two inflator modules is open. Then the voltage measured at "Driver Side Low" and "Passenger Side Low" is within a specified range. Once these conditions are met the SDM will ground "Driver Side Low" and "Passenger Side Low" through a resistor and check that "Ignition 1" is in the normal operating voltage range. When all previous conditions are met and the voltage measured at "Driver Side Low" and at "Passenger Side Low" is above a specified value, DTC 25 will set.

ACTION TAKEN:
SDM turns On the AIR BAG warning lamp, sets DTC 25 and also DTC 71. A short from ignition or B+ to either initiator circuit will damage the SDM.

DTC WILL CLEAR WHEN:
The malfunction is not longer occurring and the ignition switch is turned Off, however, DTC 71 will remain current.

DTC CHART TEST DESCRIPTION:
Number(s) below refer to step number(s) on the diagnostic chart.
1. This test determines whether the malfunction is occurring in the driver inflator module circuitry.
2. This test determines whether the malfunction is occurring in the passenger inflator module circuitry.
4. This test checks for a short from "Driver Side High" to B+ or ignition.
6. This test checks for a short from "Driver Side Low" to B+ or ignition.
8. This test checks for a short from "Passenger Side High" to B+ or ignition.
10. This test checks for a short from "Passenger Side Low" to B+ or ignition.

DIAGNOSTIC AIDS:
An intermittent condition is likely to be caused by a short to B + or ignition in the inflator module circuits. A DTC 25 history would be accompanied by DTC 71 current. A careful inspection of the circuits and components indicated on DTC 25 charts is essential to ensure that the replacement SDM will not be damaged.

Was the "SIR Diagnostic System Check" performed?

When measurements are requested in this chart, use (Saturn Tool) SA 91114NE DVM with correct terminal adapter from SA 9206Z.

NOTE: When DTC 25 has been set it is necessary to replace the SDM. Setting DTC 25 will also cause DTC 71 to set. When a Saturn Portable Diagnostic (Scan) (PDT) Tool "Clear Codes" command is issued and the malfunction is still present, diagnostic trouble codes 25 and 71 will remain current. When a PDT "Clear Codes" command is issued and malfunction is no longer present, DTC 25 will clear but DTC 71 will remain current. Ensure that the short to B+ condition is repaired prior to installing a replacement SDM to avoid damaging the ADM.