Circuit Description
When you first turn the ignition switch to the RUN position, the inflatable restraint sensing and diagnostic module (SDM) performs tests in order to diagnose critical malfunctions within the module. Next the SDM measures the ignition positive voltage, the 23 VLR and the deployment loop voltages in order to ensure that the voltages are within the respective normal voltage ranges. The SDM proceeds to continuous monitoring. The SDM contains a resistor network connected to 5 volts, the ground, and to the SDM front end sensor signal terminal 9. The 1.0 K ohms resistor in the inflatable restraint front end discriminating sensor parallel to the normally open switch provides a parallel path to ground. This causes a specified percentage of voltage in order to appear at the SDM front end sensor signal input. The SDM monitors this voltage in order to detect shorts to ground or a closed discriminating sensor.
Conditions for Setting the DTC
| • | The SDM is configured for an inflatable restraint front end discriminating sensor. |
| • | The voltage at front end sensor signal terminal 9 is less than 0.5 volts for 500 milliseconds. |
The continuous monitoring test inspects for this DTC. This test occurs when the 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 turns ON the AIR BAG Warning Indicator. |
Conditions for Clearing the MIL/DTC
| • | Current DTC |
| The voltage at the front end sensor signal terminal 9 is more than 2.4 volts for 500 milliseconds. |
| • | History DTC |
| - | You issue a scan tool CLEAR CODES command. |
| - | 250 malfunction free ignition cycles have occurred. |
Diagnostic Aids
A short to ground in the inflatable restraint front end discriminating sensor circuit may cause an intermittent condition. Inspect CKT 1834 carefully for cut or chafed wires.
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 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 checks for a malfunctioning discriminating sensor.
-
This test checks for a short-to-ground in CKT 1834.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the SIR Diagnostic System Check performed? | -- | ||
Is the resistance reading more than the specified value? | 950 ohms | |||
3 | Replace the inflatable restraint front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement . Is the repair complete? | -- | -- | |
Is the resistance reading less than the specified value? | OL | |||
5 | Repair a short to ground condition in CKT 1834. Is the repair complete? | -- | -- | |
6 | Reconnect all the SIR system components, make sure all the components are properly mounted. Have all the SIR components been reconnected and properly mounted? | -- | -- | |
7 | Clear all the SIR DTCs. Have all the SIR DTCs been cleared? | -- | -- |
