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 BELT HIGH and the PASSENGER BELT LOW.

^ Uses the measured voltage to calculate the resistance of the passenger 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 Bags Arming and Disarming for enable/disable procedures.

CONDITIONS FOR SETTING THE DTC

The following conditions can cause DTC 38 to set: The passenger seat belt side buckle pretensioner deployment loop resistance is less than 1.0 ohms. The passenger seat belt side buckle pretensioner deployment loop consists of the following components.

^ Passenger seat belt side buckle pretensioner.

^ Harness wiring of CKT AB900 (and AB950 if the vehicle is equipped with side air bags).

^ Harness wiring of CKT XB901 (and XB950 if the vehicle is equipped with side air bags).

^ 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

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 38 to set are no longer existing, History DTC 38 will set. History DTC 38 may be cleared using the scan tool.

DIAGNOSTIC AIDS

The following can cause an intermittent condition:

A short circuit between CKT AB900 (or AB950 if the vehicle is equipped with side air bags) and XB901 (and XB950) if the vehicle is equipped with side air bags).

Inspect CKTs AB900 (or AB950 if the vehicle is equipped with side air bags) and XB901 (and XB950) if the vehicle is equipped with side air bags) carefully for cutting and/or chafing. The diagnostic table directs the technician to note the value of RH PRETENS. RESIST. Comparing the value of RH 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.

2. This test determines the deployment loop resistance measured by the inflatable restraint sensing and diagnostic module.

8. This test checks for proper contact or corrosion of the SDM connector.

13. This test checks for a short from CKT AB900 or AB950 to CKT XB901 or XB950.

15. This test checks for a short in the driver pretensioner seat harness.

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.