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. Next the SDM measures IGNITION 1, 23 VLR and the deployment loop voltages to make sure they are within their respective normal voltage ranges. Then the SDM proceeds to Continuous Monitoring. The SDM contains a resistor network connected to 5 volts, ground, and to the SDM front-end sensor signal terminal 9. The 1.0 K ohm 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 to appear at the SDM front-end sensor signal input. The SDM monitors this voltage 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 checks for this DTC. This test occurs 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 ON the AIR BAG warning lamp. |
Conditions for Clearing the DTC
| • | Current DTC |
| The voltage at 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. |
| - | Once 250 malfunction free ignition cycles have occurred. |
Diagnostic Aids
A short-to-ground in the inflatable restraint front end discriminating sensor circuit can cause an intermittent condition. Inspect CKT 1834 carefully for cutting or chafing.
When measurements are requested in this table, use the J 39200 Digital Multimeter with the correct terminal adapter from the 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 the J-38125 Terminal Repair Kit. 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 . Are the repairs complete? | -- | -- | |
Is the resistance reading less than the specified value? | OL | |||
5 | Repair a short-to-ground condition in CKT 1834. Are the repairs 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? | -- | -- |
