Supplemental Inflatable Restraint (SIR)

Wiring Diagram:

CIRCUIT DESCRIPTION
The inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) performs tests to diagnose critical malfunctions within itself when the ignition switch is turned ON. The SDM monitors the six firing loops to detect leakage currents to ground and system voltage in the frontal and side air bag inflator module and seat belt pretensioner circuits. The deployment loop resistances are measured to ensure they are within their respective normal resistance ranges. The SDM does the following during one portion of the RESISTANCE MEASUREMENT test:

^ Measure the voltage difference between the DRIVER BELT HIGH and the DRIVER BELT LOW.
^ Uses the measured voltage to calculate the resistance of the driver pretensioner deployment loop.

Upon passing these tests, and if the energy reserve is charged up, the firing transistors are tested. The SDM then goes into Continuous Monitoring mode. The SDM service wait time is 1 minute. Refer to Air Bag(s) Arming and Disarming.


CONDITIONS FOR SETTING THE DTC
The driver seat belt pretensioner deployment loop resistance is more than 4.4 ohms. The driver seat belt side buckle pretensioner deployment loop consists of the following components:

^ The driver seat belt side buckle pretensioner.
^ The harness wiring of CKT AM900 (AM950 it vehicle has side air bags).
^ The harness wiring of CKT XM901 (XM950 if vehicle has side air bags).
^ The connector terminal contact.

The RESISTANCE MEASUREMENT test checks for this malfunction. This test
only occurs continuously during each ignition cycle when the IGNITION is within the normal operating voltage range.

ACTION TAKEN WHEN THE DTC SETS
^ The SDM sets a diagnostic trouble code.
^ The SDM turns ON the AIR BAG warning lamp.

CONDITIONS FOR CLEARING THE DTC
Current and History DTC codes must be cleared using a scan tool Clear DTC Information command. If the circuit fault has been successfully repaired and the conditions which caused the DTC to set are no longer existing, the DTC may be cleared using the scan tool. If the resistance in the driver seat belt side buckle pretensioner circuit is less than 4.4 ohms, a Current DTC 35 will change to a History DTC 35, which may be cleared using the scan tool.

DIAGNOSTIC AIDS
A poor connection can cause an intermittent condition. Check the following for a poor connection:

^ The 8-way driver seat connector C315A terminals 1 and 2.
^ The SDM terminals 8 and 9.
^ The wire to terminal connections in CKT AM900 (AM950 if vehicle has side air bags).
^ The wire to terminal connections in CKT XM901 (XM950 if vehicle has side air bags).
^ The driver seat belt side buckle pretensioner integral 2-way connector.

nspect CKTs and AM900 and XM901 (AM950 and XM950 if vehicle has side air bags) carefully for cutting and/or chafing. The diagnostic table directs the technician to note the entry value of the LH PRETENS. RESIST. Comparing the value of the LH PRETENS. RESIST. over multiple ignition cycles can be helpful in determining if an intermittent condition exists.

When measurements are requested in this table, use J 39200 in Tools and Equipment.


TEST DESCRIPTION
The numbers below refer to step numbers on the diagnostic table.

12. This test determines whether the malfunction is in CKT AM900 or CKT AM950 between the SDM harness connector and C315.
14. This test determines whether the malfunction is in CKT XM901 or CKT XM950 between the SDM harness connector and C315.
16. This test determines whether the malfunction is in the driver pretensioner belt assembly. This is done by substituting the known good resistance of the load tool and then observing if the malfunction is still present.
18. This test determines if the malfunction is in CKT AM900 in the driver pretensioner seat harness.
20. This test determines if the malfunction is in CKT XM901 in the driver pretensioner seat harness.