Supplemental Inflatable Restraint (SIR)

Diagnostic Chart:

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 FRONTAL HIGH and the DRIVER FRONTAL LOW.
^ Uses the measured voltage to calculate the resistance of the driver 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 deployment loop resistance is more than 6.0 Ohms. The driver deployment loop consists of the following components:

^ The inflatable restraint steering wheel module.
^ The inflatable restraint steering wheel module coil.
^ The harness wiring of CKT BM30.
^ The harness wiring of CKT B30.
^ The connector terminal contact.

The RESISTANCE MEASUREMENT test checks for this malfunction. This test only occurs once 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
The resistance of the driver deployment loop is less than 6.0 ohms. You must issue a scan tool Clear Codes command to clear a Current or History code.

Diagnostic Aids
A poor connection can cause an intermittent condition. Check the following for a poor connection:

^ Check the inflatable restraint steering wheel module coil integral 2-way connector terminals 1 and 2.
^ Check the inflatable restraint steering wheel module coil connector terminals 7 and 8.
^ Check the SDM terminals 1 and 2.
^ Check the wire to terminal connections in CKT BM30.
^ Check the wire to terminal connections in CKT B30.

The diagnostic table directs the technician to note the entry value of the Driver Air Bag Resistance. Comparing the value of the Driver Air Bag Resistance over multiple ignition cycles can be helpful in determining if an intermittent condition exists.

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

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 in CKT BM30.
14. This test determines whether the malfunction is in CKT B30.