DTC 73

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. 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 ignition is within normal operating voltage range.
^ The measured leakage currents to system voltage in or the loop resistance of the driver Side Impact Sensor (SIS) loop are above a specified value caused by:

- A short circuit from the driver Side Impact Sensor (SIS) loop to system voltage.
- An open circuit or high resistance condition in the driver Side Impact Sensor (SIS) loop.

The driver Side Impact Sensor (SIS) loop consists of the following components:

^ The inflatable restraint Side Impact Sensor (LH).
^ The harness wiring of CKT B41.
^ The harness wiring of CKT B42.
^ The harness wiring of CKT XB42.
^ The connector terminal contact.

DTC 73 will set once one of these conditions is met. This test is run during the SDM Turn-ON tests.

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 73 to set are no longer existing, History DTC 73 will set. History DTC 73 may be cleared using the scan tool.

Diagnostic Aids
An inflatable restraint driver Side Impact Sensor (SIS) circuit short-to-ground can cause an intermittent condition. Inspect CKTs B41, B42 and XB42 carefully for cutting and/or chafing. A careful inspection of the circuits and components indicated on the DTC 73 Table is essential to make sure that the replacement SDM will not be damaged.

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

Test Description
The following numbers refer to the step numbers on the diagnostic table:

7. This test determines whether the malfunction is a short to voltage condition in CKT B42 in the LH door electrical harness.
9. This test determines whether the malfunction is a short to voltage condition in CKT XB42 in the LH door electrical harness.
11. This test determines whether the malfunction is a high resistance condition in CKT B42 in the LH door electrical harness.
13. This test determines whether the malfunction is a high resistance condition in CKT XB42 in the LH door electrical harness.
20. This test determines whether the malfunction is a short to voltage condition in CKT B41.
22. This test determines whether the malfunction is a short to voltage condition in CKT XB42 between the LH side door electrical connector and the SDM harness connector.
24. This test determines whether the malfunction is a high resistance condition in CKT B41.
26. This test determines whether the malfunction is a high resistance condition in CKT XB42 between the LH side door electrical connector and the SDM harness connector.