Circuit Description
When you first turn the ignition switch to the RUN position, the supplemental restraint sensing and diagnostic module (SDM) performs tests in order to diagnose critical malfunctions within the SDM. The SDM measures the following circuits in order to ensure that they are within their respective normal voltage ranges:
| • | IGNITION 1 |
| • | Deployment loop voltages |
Then, the SDM proceeds with the RESISTANCE MEASUREMENT test. During one portion of the RESISTANCE MEASUREMENT test, the SDM performs the following steps:
| • | Grounds the DRIVER SIDE LOW terminal 3 through an internal current sink |
| • | Connects the DRIVER SIDE HIGH terminal 2 to an internal constant current source which produces proportional voltage drops in the deployment loop. |
| • | Measures the voltage difference between DRIVER SIDE HIGH and DRIVER SIDE 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 deployment loop is not shorted to ground. |
| • | The driver deployment loop resistance is more than 3.8 ohms. |
| The driver deployment loop consists of the following components: |
| - | The supplemental restraint steering wheel module. |
| - | The supplemental restraint steering wheel module coil. |
| - | The harness wiring of CKT 347 |
| - | The harness wiring of CKT 348 |
| - | The connector terminal contact |
The RESISTANCE MEASUREMENT test inspects for this malfunction. This test only occurs once each ignition cycle when IGNITION 1 is within the normal operating voltage range.
Action Taken When the DTC Sets
| • | The SDM sets a diagnostic trouble code. |
| • | The SDM turns the AIR BAG warning lamp to the ON position. |
Conditions for Clearing the DTC
The DTC will clear when one of the following conditions are met:
| • | Current DTC |
| - | The resistance of the driver deployment loop is less than 3.8 ohms. |
| - | The ignition switch is cycled. |
| • | History DTC |
| - | You issue a scan tool CLEAR CODES command. |
| - | After 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 may cause an intermittent condition. Inspect the following items for a poor connection:
| • | The supplemental restraint steering wheel module steering column connector terminals A and B |
| • | The upper supplemental restraint steering wheel module coil connector terminals A and B |
| • | The SDM terminals 2 and 3 |
| • | The wire to terminal connections in CKT 347 |
| • | The wire to terminal connections in CKT 348 |
The diagnostic table directs the technician to note the entry value of DRIVER RESISTANCE. Comparing the value of DRIVER RESISTANCE over multiple ignition cycles may be helpful in determining if an intermittent condition exist.
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 an inspection for proper connection is requested, refer to Intermittents and Poor Connections . 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 deployment loop resistance measured by the supplemental restraint sensing and diagnostic module (SDM).
-
This test inspects for proper contact or corrosion of the yellow 2-way connector.
-
This test isolates the malfunction to one side of the supplemental restraint steering wheel module yellow 2-way connector.
-
This test determines whether the malfunction is due to the supplemental restraint steering wheel module or the module coil.
-
This test inspects 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 SRS Diagnostic System Check performed? | -- | Go to Step 2 | |
Has the DRIVER RESISTANCE been read and recorded on the repair order? | -- | Go to Step 3 | -- | |
Are the terminals damaged or corroded? | -- | Go to Step 4 | Go to Step 6 | |
4 | Replace the yellow 2-way harness connector at the base of the steering column. Refer to Wiring Repair . Is the repair complete? | -- | Go to Step 5 | -- |
5 | Inspect for proper connection at terminals A and B of the supplemental restraint steering wheel module coil side of the connector. Are the terminals damaged or corroded? | -- | Go to Step 7 | Go to Step 23 |
6 | Inspect for proper connection at terminals A and B of the supplemental restraint steering wheel module coil side of the connector. Are the terminals damaged or corroded? | -- | Go to Step 7 | Go to Step 8 |
7 | Replace the supplemental restraint IP module coil. Refer to Supplemental Restraint Steering Wheel Module Coil Replacement . Is the repair complete? | -- | Go to Step 23 | -- |
8 |
Is DRIVER RESISTANCE more than the specified value? | 3.8 ohms | Go to Step 10 | Go to Step 9 |
9 |
Is the repair complete? | -- | Go to Step 23 | -- |
Is DRIVER RESISTANCE more than the specified value? | 3.8 ohms | Go to Step 14 | Go to Step 11 | |
Is DRIVER RESISTANCE more than the specified value? | 3.8 ohms | Go to Step 13 | Go to Step 12 | |
12 |
Is the repair complete? | -- | Go to Step 23 | -- |
13 |
Is the repair complete? | -- | Go to Step 23 | -- |
Is the connector damaged or corroded? | -- | Go to Step 15 | Go to Step 17 | |
15 | Replace the SDM harness connector. Refer to Wiring Repair . Is the repair complete? | -- | Go to Step 16 | -- |
16 | Inspect for proper connection at terminal 2 and terminal 3 on the SDM. Are the terminals damaged or corroded? | -- | Go to Step 18 | Go to Step 23 |
17 | Inspect for proper connection at terminal 2 and terminal 3 on the SDM. Are the terminals damaged or corroded? | -- | Go to Step 18 | Go to Step 19 |
18 | Replace the SDM. Refer to Supplemental Restraint Sensing and Diagnostic Module Replacement . Is the repair complete? | -- | Go to Step 23 | -- |
Is the resistance reading within the specified values? | 0-0.5 ohms | Go to Step 21 | Go to Step 20 | |
20 | Repair the high resistance condition in CKT 347. Is the repair complete? | -- | Go to Step 23 | -- |
Measure the resistance from the SDM harness connector terminal 3 to the supplemental restraint steering wheel module yellow 2-way harness connector terminal B. Is the resistance reading within the specified values? | 0-0.5 ohms | Go to Step 22 | ||
22 | Repair the high resistance condition in CKT 348. Is the repair complete? | -- | Go to Step 23 | -- |
23 |
Have all of the SRS components been reconnected and properly mounted? | -- | Go to Step 24 | -- |
24 | Clear all the SRS DTCs. Have all the SRS DTCs been cleared? | -- | -- |
