Supplemental Inflatable Restraint (SIR)

Wiring Diagram:

CIRCUIT DESCRIPTION
The inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) performs Turn-On 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. Then, the SDM proceeds with the Resistance Measurement test to measure the deployment loop resistances to ensure they are within their respective normal resistance ranges. 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 frontal air bag deployment loop resistance is less than 1.7 ohms. The driver frontal air bag deployment loop consists of the following components.

^ Inflatable restraint steering wheel module.
^ Inflatable restraint steering wheel module coil.
^ Harness wiring of CKT BM30.
^ Harness wiring of CKT B30.
^ Connector terminal contacts, including shorting bars.

The deployment loop resistance test checks for this malfunction.

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
The resistance of the driver deployment loop is greater than 1.7 ohms. 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 Current DTC 32 to set are no longer existing, History DTC 32 will set. History DTC 32 may be cleared using the scan tool.

DIAGNOSTIC AIDS
The following can cause an intermittent condition:

^ A short circuit between CKTs BM30 and B30.
^ A malfunctioning shorting bar in the inflatable restraint steering wheel module.
^ A malfunctioning shorting bar in the inflatable restraint steering wheel module coil.
^ A malfunctioning shorting bar on the inflatable restraint SDM harness connector above SDM harness connector terminals 1 and 2.

Inspect CKTs BM30 and B30 carefully for cutting and/or chafing. The diagnostic table directs the technician to note the value of DRIVER AIR BAG RES. Comparing the value of DRIVER AIR BAG RES. 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.

3. This test determines whether the malfunction is in the inflatable restraint steering wheel module. This is done by substituting the known good resistance of the inflatable restraint steering wheel module. Then, observing if the malfunction is still present.
5. This test determines whether the malfunction is in the inflatable restraint steering wheel module coil.
12. This test determines whether the malfunction is between CKT BM30 and CKT B30.