Circuit Description
The inflatable restraint sensing and diagnostic module (SDM) monitors the inflatable restraint front end discriminating sensor circuit for front impact detection. The SDM processes the signal provided by the front end discriminating sensor to further support deployment of the air bags. The front end discriminating sensor is an input only to the SDM and does not directly cause air bag deployment. When the ignition is turned ON, the SDM performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity and for shorts to ground or voltage. If a malfunction is detected, a DTC will be stored.
Conditions for Running the DTC
Ignition 1 voltage is within the normal operating voltage range.
Conditions for Setting the DTC
The SDM detects the voltage at the front end discriminating sensor signal input is 0.5 volts or less for 500 milliseconds.
Action Taken When the DTC Sets
| • | The SDM disables the front end discriminating sensor input. |
| • | The SDM commands ON the AIR BAG indicator via Class 2 serial data. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | You issue a scan tool CLEAR DTCs command. |
| • | A history DTC will clear once 255 malfunction free ignition cycles have occurred. |
Diagnostic Aids
A broken or chafed wire in the front end discriminating sensor circuit may cause an intermittent condition to occur. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
Tests for a malfunctioning front end discriminating sensor.
-
Tests for a short to ground in the front end discriminating sensor signal circuit.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: SIR Schematics Connector End View Reference: SIR Connector End Views | ||||
1 | Did you perform A Diagnostic System Check - SIR? | -- | Go to Step 2 | |
2 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 3 |
3 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 4 |
4 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 5 |
Does the resistance measure more than the specified value? | 950 ohms | Go to Step 6 | Go to Step 7 | |
Test the discriminating sensor signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 | |
7 | Replace the front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
