Supplemental Inflatable Restraint (SIR)

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION
During normal, non-deployment operation of the SIR system, a small amount of current flows through both the driver and passenger deployment loops. The diagnostic resistors within the dual pole arming sensor and the discriminating sensors along with the resistance of the inflator modules cause voltage drops within the deployment loops. The DERM monitors the voltages at "Driver Side Low" terminal "B8" and "Passenger Side Low" terminal "B7" to detect shorts or opens within the deployment loops. When the measured voltage at terminal "B8," or "B7" is below a specified percentage of its respective 36 VLR power supply voltage for 500 milliseconds DTC 24 is set.

DTC WILL SET WHEN
The voltage measured at "Driver Side Low" terminal "B8" is below a specified percentage of "Driver 36 VIR" or when the voltage measured at "Passenger Side Low" terminal "B7" is below a specified percentage of "Passenger 36 VLR" for 500 milliseconds. This test is run during the "Continuous Monitoring" test.

ACTION TAKEN
DERM sets a diagnostic trouble code and sends a command to the instrument cluster to turn "ON" the "AIR BAG" warning lamp.

DTC WILL CLEAR WHEN
The voltage measured at "Driver Side Low" terminal "B8" is within a specified percentage of "Driver 36 VLR" and the voltage measured at "Passenger Side Low" terminal "B7" is within a specified percentage of "Passenger 36 VLR" for 500 milliseconds.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test determines whether the malfunction is occurring in the steering column circuitry.
2. This test determines whether the malfunction is occurring in the passenger inflator module circuitry.
3. This test checks for a partial short across the diagnostic resistor in the forward discriminating sensor.
4. This test checks for a partial short across the diagnostic resistor in the passenger compartment discriminating sensor.
5. This test checks for a short from the discriminating sensor interconnect circuit, the low side of the driver deployment loop and the low side of the passenger deployment loop to ground.
6. This test checks for a short from the high side of the driver deployment loop to ground.
7. This test checks for a short from the high side of the passenger deployment loop to ground.
8. This test checks for an open in the driver deployment loop diagnostic resistor of the dual pole arming sensor.
9. This test checks for an open in the passenger deployment loop diagnostic resistor of the dual pole arming sensor.
10. This test checks for high resistance in the "Driver 36 VLR" circuit.
11. This test checks for high resistance in the "Passenger 36 VLR" circuit.
12. This test checks for an open in the high side of the driver deployment loop.
13. This test checks for an open in the high side of the passenger deployment loop.

DIAGNOSTIC AIDS
An intermittent condition is likely to be caused by a poor connection at DERM terminals "A3" and "A4," dual pole arming sensor terminals "B," "C," "E," or "G," a malfunctioning dual pole arming sensor, a malfunctioning discriminating sensor, an open in CKT 1403B or CKT 347B, a short to ground in CKT 347, CKT 348, CKT 349, CKT 1403 or CKT 1404, high resistance in CKT 236 or CKT 1401, a malfunctioning SIR coil assembly or a malfunctioning passenger inflator module. Refer to DTC 25 to diagnose a possible short to B+. When the malfunction occurs during an ignition cycle DTC 24 will set. If the malfunction is present at the beginning of the next ignition cycle DTC 25 will set and DTC 24 will be moved to a history file. Supplemental Inflatable Restraint (SIR)