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 FRONTAL LOW terminal 9 through an internal current sink. |
| • | Connects the DRIVER FRONTAL 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 FRONTAL HIGH and DRIVER FRONTAL LOW. |
| • | Calculates the resistance of the driver frontal deployment loop using the measured voltage. |
Conditions for Setting the DTC
| • | The driver and passenger frontal deployment loops are not open. |
| • | The driver and passenger frontal deployment loops are not shorted to voltage. |
| • | The driver and passenger frontal deployment loops are not shorted to ground. |
| • | The driver frontal deployment loop resistance is more than 3.8 ohms. The driver frontal 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
The DTC will clear when one of the following conditions is met:
| • | Current DTC |
| The resistance of the driver frontal deployment loop is less than 3.8 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
A poor connection can cause an intermittent condition. Check the following for a poor connection:
| • | The inflatable restraint steering wheel module steering column connector terminals A and B. |
| • | The upper inflatable restraint steering wheel module coil connector terminals A and B. |
| • | The SDM terminals 10 and 9. |
| • | The wire to terminal connections in CKT 347. |
| • | The wire to terminal connections in CKT 348. |
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 proper contact or corrosion of the yellow 2-way connector.
-
This test isolates the malfunction to one side of the inflatable restraint steering wheel module 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 proper contact or corrosion of the SDM connector.
-
This test determines whether the malfunction is in CKT 347.
-
This test determines whether the malfunction is in CKT 348.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the SIR Diagnostic System Check performed? | -- | ||
Are the terminals damaged or corroded? | -- | |||
3 | Check for proper connection at terminals A and B of the inflatable restraint steering wheel module harness side of the connector. Are the terminals damaged or corroded? | -- | ||
4 | Check for proper connection at terminals A and B of the inflatable restraint steering wheel module coil side of the connector. Are the terminals damaged or corroded? | -- | ||
5 | Replace the yellow 2-way harness connector C207 at the base of the steering column. Refer to Wiring Repair . Are the repairs complete? | -- | -- | |
6 | Replace the inflatable restraint steering wheel module coil. Refer to Steering. Are the repairs complete? | -- | -- | |
7 |
Is DTC B1121 current? | -- | ||
8 |
Are the repairs complete? | -- | -- | |
Is DTC B1121 current? | -- | |||
Is DTC B1121 current? | -- | |||
11 |
Are the repairs complete? | -- | -- | |
12 |
Are the repairs complete? | -- | -- | |
Is the connector damaged or corroded? | -- | |||
14 | Replace the SDM harness connector. Refer to Wiring Repair . Are the repairs complete? | -- | -- | |
15 | Check for proper connection at terminal 9 and terminal 10 on the SDM. Are the terminals damaged or corroded? | -- | ||
16 | Check for proper connection at terminal 9 and terminal 10 on the SDM. Are the terminals damaged or corroded? | -- | ||
17 | Replace the inflatable restraint sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement . Are the repairs complete? | -- | -- | |
Is the resistance reading within the specified values? | 0-0.5 ohms | |||
19 | Repair the high resistance condition in CKT 347. Are the repairs complete? | -- | -- | |
Is the resistance reading within the specified values? | 0-0.5 ohms | |||
21 | Repair the high resistance condition in CKT 348. Are the repairs complete? | -- | -- | |
22 | Reconnect all the SIR system components, make sure all the components are properly mounted. Have all the SIR components been reconnected and properly mounted? | -- | -- | |
23 | Clear all the SIR DTCs. Have all the SIR DTCs been cleared? | -- | -- |
