Circuit Description
When you first turn the ignition switch to the ON position, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. Upon passing these tests Ignition 1, 23VLR and the deployment loop voltages are measured to make sure they are within their respective normal voltage ranges. The SDM monitors the voltages at Driver Frontal Low terminal 9 and Passenger Frontal Low terminal 8 to detect shorts to voltage in the inflator module circuits.
Conditions for Setting the DTC
The voltage at Driver Frontal Low terminal 9 or Passenger Frontal Low terminal 8 is more than 4.0 volts for 500 milliseconds. The following tests check for this DTC. These tests occur when Ignition 1 is within the normal operating voltage range.
| • | Power-On--When the malfunction is detected in this test, the Resistance Measurement test will not be performed. |
| • | Continuous Monitoring |
Action Taken When the DTC Sets
| • | The SDM sets a diagnostic trouble code. |
| • | The SDM commands the instrument cluster (IPC) to turn ON the AIR BAG warning lamp. |
Conditions for Clearing the MIL/DTC
| • | The voltage measured at Driver Frontal Low and Passenger Frontal Low is below 4.0 volts for 500 milliseconds. |
| • | The ignition switch is turned OFF. |
| • | DTC B1171 will remain Current. |
Diagnostic Aids
A short to voltage in the inflatable restraint steering wheel module circuit or the passenger inflator module circuit can cause an intermittent condition. Moving wires while monitoring Driver Frontal Senselo and Passenger Frontal Senselo may help to locate the fault. Inspect CKT 347, CKT 348, CKT 1403, and CKT 1404 carefully for cutting or chafing. The diagnostic table directs the technician to note the entry value of Driver Frontal Senselo and Passenger Frontal Senselo. Noting the value of Driver Frontal Senselo and Passenger Frontal Senselo during diagnosis can be helpful in determining if an intermittent condition exists.
When measurements are requested in this table, use J 39200 Digital Multimeter with the correct terminal adapter from J 35616 Connector Test Adapter Kit. When a check for proper connection is requested, refer to General Electrical Diagnosis Procedures in Wiring Systems. When a wire, connector or terminal repair is requested, use J-38125 Terminal Repair Kit and refer to Wiring Repair .
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This test determines the Driver Frontal Low voltage measured by the inflatable restraint sensing and diagnostic module (SDM) and if the malfunction is currently occurring.
-
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 determines whether the malfunction is in CKT 347.
-
This test determines whether the malfunction is in CKT 348.
-
This test isolates the malfunction to one side of the inflatable restraint IP module, yellow 2-way connector.
-
This test determines whether the malfunction is in CKT 1404.
-
This test determines whether the malfunction is in CKT 1403.
Important: To avoid damaging a replacement SDM, the short to voltage must be repaired prior to installation.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the SIR Diagnostic System Check performed? | -- | ||
Is Driver Frontal Senselo more than the specified value? | 4.0 V | |||
Is Driver Frontal Senselo more than the specified value? | 4.0 V | |||
Is Driver Frontal Senselo more than the specified value? | 4.0 V | |||
5 |
Have the repairs been completed? | -- | -- | |
6 |
Have the repairs been completed? | -- | -- | |
Is the voltage reading less than the specified value? | 1.0 V | |||
8 | Repair a short to voltage condition in CKT 347. Refer to Wiring Repair . Have the repairs been completed? | -- | -- | |
Using J 39200 DMM, measure the voltage on the SDM harness connector from terminal 9 to terminal 18. Is the voltage reading less than the specified value? | 1.0 V | |||
10 | Repair a short to voltage condition in CKT 348. Refer to Wiring Repair . Have the repairs been completed? | -- | -- | |
Is Passenger Frontal Senselo more than the specified value? | 4.0 V | |||
12 |
Have the repairs been completed? | -- | -- | |
Is the voltage less than the specified value? | 1.0 V | |||
14 | Repair a short to voltage condition in CKT 1404. Refer to Wiring Repair . Have the repairs been completed? | -- | -- | |
Using J 39200 DMM, measure the voltage on the SDM harness connector from terminal 7 to terminal 18. Is the voltage less than the specified value? | 1.0 V | |||
16 | Repair a short to voltage condition in CKT 1403. Refer to Wiring Repair . Have the repairs been completed? | -- | -- | |
17 | An intermittent short to voltage condition caused DTC B1125 to set. Use the Diagnostic Aids for DTC B1125 and this table to find the intermittent short to voltage. Has the intermittent short to voltage been found and repaired? | -- | -- | |
18 |
Have all the SIR components been reconnected and properly mounted? | 4.0 V | -- |
