Circuit Description
When you first turn the ignition switch to the RUN position, the inflatable restraint Sensing and Diagnostic Module (SDM) performs tests to diagnose critical malfunctions within itself. Next the SDM measures Ignition Positive Voltage and the deployment loop voltages to make sure they are within their respective normal voltage ranges. Then the SDM proceeds with the RESISTANCE MEASUREMENT test. During one portion of the RESISTANCE MEASUREMENT test, the SDM does the following:
| • | Grounds the DRIVER LOW terminal 9 through an internal current sink. |
| • | Connects the DRIVER HIGH terminal 10 to an internal constant current source. This current produces proportional voltage drops in the deployment loop. |
| • | Measures the voltage difference between DRIVER HIGH and DRIVER LOW. |
| • | Calculates the resistance of the driver deployment loop using the measured voltage. |
Conditions for Setting the DTC
| • | The driver and passenger deployment loops are not open. |
| • | The driver and passenger deployment loops are not shorted to voltage. |
| • | The driver and passenger deployment loops are not shorted to ground. |
| • | The driver deployment loop resistance is less than 1.7 ohms. The driver deployment loop consists of the following components: |
| - | Inflatable restraint steering wheel module. |
| - | Inflatable restraint steering wheel module coil. |
| - | Harness wiring of CKT 347. |
| - | Harness wiring of CKT 348. |
| - | Connector terminal contact. |
The RESISTANCE MEASUREMENT test checks for this malfunction. This test only occurs once each ignition cycle when Ignition Positive Voltage is within the normal operating voltage range.
Action Taken When the DTC Sets
| • | The SDM sets a Diagnostic Trouble Code. |
| • | The SDM commands the Instrument Panel Cluster (IPC) to turn ON the AIR BAG warning lamp. |
Conditions for Clearing the MIL/DTC
| • | Current DTC |
| The resistance of the driver deployment loop is more than 1.7 ohms and the ignition switch is cycled. |
| • | History DTC |
| - | You issue a scan tool CLEAR CODES command. |
| - | Once 250 malfunction free ignition cycles have occurred. |
When you issue a scan tool CLEAR CODES command and the malfunction is still present, the DTC will not reappear until the next ignition cycle.
Diagnostic Aids
The following can cause an intermittent condition:
| • | A short circuit between CKT 347 and CKT 348. |
| • | A short circuit between CKT 347 and CKT 1403. |
| • | A short circuit between CKT 347 and CKT 1404. |
| • | A malfunctioning shorting bar on the inflatable restraint steering wheel module connector. |
| • | A malfunctioning shorting bar on the inflatable restraint steering wheel module coil steering column connector. |
When measurements are requested in this table, use the J 39200 DMM with the correct terminal adapter from the J 35616 Connector Test Adapter Kit. When an inspection for proper connection is requested, refer to Testing for Electrical Intermittents in Wiring Systems. When a wire, connector or terminal repair is requested, use the J-38125 Terminal Repair Kit and refer to Wiring Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This test checks for a short from CKT 1403 to CKT 347.
-
This test isolates the malfunction to one side of the inflatable restraint steering wheel module coil yellow 2-way connector.
-
This test determines whether the malfunction is due to the inflatable restraint steering wheel module or the module coil.
-
This test checks for a short from CKT 347 to CKT 348.
-
This test checks for a short from CKT 347 to CKT 1404.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the SIR Diagnostic System Check performed? | -- | ||
Is DTC B1116 also present? | -- | |||
3 |
Are the repairs complete? | -- | -- | |
Is DTC B1122 current? | -- | |||
Is DTC B1122 current? | -- | |||
6 |
Is DTC B1122 current? | -- | ||
7 |
Are the repairs complete? | -- | -- | |
8 |
Are the repairs complete? | -- | -- | |
Is the resistance reading less than the specified value? | OL | |||
10 | Repair a short from CKT 347 to CKT 348. Are the repairs complete? | -- | -- | |
Measure the resistance from the SDM harness connector terminal 10 to terminal 8. Is the resistance reading less than the specified value? | OL | |||
12 | Repair a short from CKT 347 to CKT 1404. Are the repairs complete? | -- | -- | |
13 | Reconnect all the SIR system components, make sure all the components are properly mounted. Have all the SIR components been reconnected and properly mounted? | -- | -- | |
14 | Clear all the SIR DTCs. Have all the SIR DTCs been cleared? | -- | -- |
